More info required?

Dear ???

What kind of info are you specifically looking for?

For pictures of examples, and "prototype info hints" for further research,
I'd bookmark:
(in no particular order of preference)

-  https://www.railcarphotos.com

-  http://www.rrpicturearchives.net

-  https://www.railpictures.net

Happy Modelling,
Aim to Improve,
Prof Klyzlr

Newsprint Box Cars

I’m interested in the CPI box cars, I found some helpful info here:

http://www.nakina.net/cp/cpi.html

Thank you for your reply

For Canadian cars, go here

http://canadianfreightcargallery.ca/

Lots of photos and data on cars from the Great White North, and a fair number from the US as well.

CPI was applied to cars built in Canada and used in international service.  These CPI boxes were remarked CP at some point before 1988.

Scott Chatfield 

CP paper service boxcars

Which info are you looking for though?

(It would have been helpful to indicate Canadian Pacific in the initial post BTW).

CP had a bunch of 40' boxcars with 8' sliding doors built and assigned to newsprint/paper service in the 1950s, in the mid/late 1960s they started acquiring 50' plug door cars, which they acquired in groups through the 1970s.

You also didn't mention modeling scale you might be interested in, but there are models in HO scale of the 1967-69 inside-post NSC built cars originally run by Life-Like Proto 1000 and recently acquired by Atlas and pending a re-release, and the 1977-1980 outside-post NSC cars also by Atlas.

Some info on the 1967-69 cars, which both CP and CN rostered:

http://vanderheide.ca/blog/2019/04/05/freight-car-friday-72-cp-80967-model/

Most of the CPI cars were renumbered CP (by simply removing the "I") in the early 1980s after NAFTA apparently changed some of the customs arrangements that controlled these "International Service Only" cars. (CNA/CPAA cars was a slightly different arrangement)

CP paper service boxcars - 50' roster info

CP 80000-80499 blt. /64 Hawker-Siddeley

http://canadianfreightcargallery.ca/cgi-bin/image.pl?i=cp80097&o=cprail

CP 80500-80966 blt. /65 Hawker-Siddeley

http://canadianfreightcargallery.ca/cgi-bin/image.pl?i=cp80580&o=cprail

CP 80967-81216 blt. /67 National Steel Car (Proto1000/Atlas model)

http://canadianfreightcargallery.ca/cgi-bin/image.pl?i=cp81110&o=cprail

CPI 85001-85499 blt. /69 National Steel Car (proto1000/Atlas model)

http://canadianfreightcargallery.ca/cgi-bin/image.pl?i=cpi85232&o=cprail

CPI 85500-85634 blt. /75 National Steel Car

http://canadianfreightcargallery.ca/cgi-bin/image.pl?i=cpi85594&o=cprail

CPI 85635-85734 blt. /77 National Steel Car (Atlas model)

http://canadianfreightcargallery.ca/cgi-bin/image.pl?i=cp85718&o=cprail

QC 75000-75099 blt. /79 National Steel Car (Atlas model)

http://canadianfreightcargallery.ca/cgi-bin/image.pl?i=qc75081&o=cprail

QC 75100-75299 blt. /80 National Steel Car (Atlas model)

http://canadianfreightcargallery.ca/cgi-bin/image.pl?i=qc75206&o=cprail

CP paper service boxcars - 50' roster info 2

CP 84989-84999 ex-CP 80967-81216 series re/blt with extended height /71

http://canadianfreightcargallery.ca/cgi-bin/image.pl?i=cp84996&o=cprail

CP 84977-84988 ex-CP 80967-81216 series re/blt with extended height /72

http://canadianfreightcargallery.ca/cgi-bin/image.pl?i=cp84983&o=cprail

CPAA 89981-89999 blt. /6x Pullman-Standard ex-TLCX 40-59 /71

(no photos online as CPAA on canadianfreightcargallery.ca, rr-fallenflags.org or rrpicturearchives.net)

CPAA 89910-89980 blt. /62 Pullman-Standard ex-TLCX 1001-1075 /73

http://canadianfreightcargallery.ca/cgi-bin/image.pl?i=cpaa89958&o=cprail

CPAA 86000-86091 blt /69 National Steel Car ex-MDW 7000-7099 /87

http://canadianfreightcargallery.ca/cgi-bin/image.pl?i=cpaa86051&o=cprail

My favourite newsprint car;

My favourite newsprint car; on the left.

Don't know that UP had any

Off the top of my head I can't think of any boxcars built new for the UP that were considered newsprint cars.  Now the Mopac had some plug door boxcars that fit the basic description,  but I saw them hauling rolls of kraft paper (to make cardboard boxes), not newsprint per se.  I also saw them hauling bagged fertilizer,  because you know boxcars can haul lots of stuff.

Now after 1995 a whole new group of 110-ton plug door boxcars were built, and many of them hauled newsprint.  If memory serves the UP had a small group wearing CHTT marks, Chicago Heights Terminal & Transfer, once a Mopac subsidiary.  But were they bought to haul newsprint?   I can't say.  UP generally uses CHTT marks on cars on long-term lease.

Most "newsprint" boxcars are just clean, tight (no leaks) boxcars with single plug doors.  The Canadian ones like those the OP asked about were Plate C (11'0" inside height) cars built at a time when most boxcars were still being built to fit in Plate B.  The extra height allowed rolls of newsprint to be stacked two deep in the car.

Scott Chatfield 

UP 507406

Would this yellow door UP box car be use to carry newsprint?

Doubtful

Not a plug door.  Sliding doors are not that water tight, although you will see cars with paper around the opening to try to keep water out.  Much more common a practice before plug door boxcars were a thing.  In other words, before 1960.

A lot of the UP's 500000-series boxcars were in autoparts service.

Scott Chatfield 

Sliding Doors

Some cars with sliding doors were used in paper service - especially before plug doors became common, so era plays a big part here (and I don't see era mentioned anywhere, other than being interested in CPI cars bascially means 1970s) - CN and CP both had sliding door 40' cars that were marked for paper service, and I believe some other railways had sliding door cars assigned for paper loading as well. 

http://canadianfreightcargallery.ca/cgi-bin/image.pl?i=cn571599&o=cn (yellow doors on CN marked paper service)

http://canadianfreightcargallery.ca/cgi-bin/image.pl?i=cp58702&o=cprail (green paint and shield under the logo marked paper service on CP)

http://canadianfreightcargallery.ca/cgi-bin/image.pl?i=ont91009&o=ont (yellow oval left of door marks newsprint service)

http://canadianfreightcargallery.ca/cgi-bin/image.pl?i=ont92076&o=ont

Can all depend on grades of paper as well (magazine quality, newsprint, kraft/brown paper, boxboard, etc.).

Also cars that are in pulp service are actually better off with sliding doors (and modern pulp service cars have vents added to the body) as the pulp is usually high in moisture.

However, paper cars tended to be clean but plain, smooth-walled interiors. That UP car with the "DF" (for "Damage Free" (brand name) interior loading/restraint devices) is not likely to be used for paper, with belt rails and tie downs in the car walls.

CPI/CPAA International Markings

Since this thread is on the topic of CPI marked boxcars...

CP was obviously Canadian Pacific's standard reporting mark. As a Canadian railway their cars could be used in unrestricted domestic traffic within Canada, and cross-border traffic to the US, but couldn't stay in the foreign country and be used for domestic loads in the US under import regulations.

CPI marks applied to a couple groups of newsprint cars (and other types of cars) were used through the late 1960s to early 1980s were used to identify Canadian-built cars that were assigned under some customs regulation I don't really understand to "International Service Only" - they were supposed to only be loaded in cross-border traffic and not domestic loads in either country. (I'm sure this rule got violated once in a while.)

CPAA marks identified US-built/acquired cars that were considered US-domestic cars for customs purposes (i.e. no import dues paid to bring them to Canada). These could be used in an un-restricted manner in the US like other US railways' domestic cars and for cross border traffic.  An earlier version of this was marking several groups of boxcars with "International of Maine Division" lettering. 

Canadian National had similar markings, with CNIS markings for "International Service only", and CNA for American cars. CN also had several US subsidiaries: Grand Trunk Western (GTW), Central Vermont (CV) and Duluth, Winnipeg & Pacific (DWP). The later two subsidiaries also had International Service marks (CVC and DWC respectively) which were used on Canadian-built newsprint boxcars. (CN still uses GTW and DWC marks on various cars today, but this seems to be more of an accounting or business-assignment thing, as the International Service meaning is no longer there. Both US and Canadian built cars can be found with both markings today.)

As I understand it, the

As I understand it, the reason behind the various "international" reporting marks is because the US had a requirement that any foreign car that spent more than a certain amount of time in the US (e.g. more than 60 days in a calendar year), that car was considered to have been imported into the US and duties and taxes were required to be paid for it.  Once those were paid, the car could spend any amount of time in the US.  This left the Railways with 3 choices:

1. Pay foreign taxes and duties on a large block of their fleet, including cars that may never cross the border in their lifetime (expensive)
2. Keep meticulous records of each car that crossed the border, and try to manage customer loading for cars close to the limit (paperwork nightmare)
3. Create a separate reporting mark for a much smaller group of cars, pay duties and taxes on them, which allows unrestricted travel in either country

For certain types of cars, (paper, lumber, auto parts, potash) that naturally do a lot of international travel, option 3 is the best one.  Keep in mind that all cars can still be used internationally, they just cross the border infrequently.

Another use for international markings is to use a regulation that allowed for not paying duties/taxes in either country as long as the car was only used for international service.  Kind of like Duty Free shops at airports - you don't pay tax as long as you don't consume the product domestically.

And then as Chris mentioned, they are also used to identify cars built or purchased in the US, either for primarily US use or with full taxes paid for unrestricted international use.

I think Canada had a similar customs requirement for US cars, but that wasn't as much of an issue for US roads.

It was either the original Free Trade Agreement or an amendment which abolished these customs regulations, and allowed essentially unrestricted international travel for all cars.  The special reporting marks then were used to identify cars designated or preferred for certain international usage.

Interesting aside: Back in the late 80's or very early 90's, a foreign unit came into Winnipeg on a CN train from International Falls that was supposed to be removed before the train crossed the border.  I forget what it was exactly but it was an unusual unit, maybe an Amtrak F40.  It was missing some piece of documentation - either the FRA certificate or waiver or something - so US customs would not allow the unit back into the US.  It sat in Winnipeg for several weeks while higher-ups tried to figure out how to get it returned.  It was reported that several of those folks were getting worried because it was getting real close to that time limit and if they didn't get it returned, someone was going to have to pay a hefty duty and tax bill to Canadian Customs.

Craig

3. Create a separate

The thing is, those International Service cars (CPI, CNIS) were specifically stencilled to NOT use them in domestic service in either country. Only cross-border.