The car was originally Denver and Rio Grande #63383 and exists today at the Western Railway Museum in Rio Vista California. In 1944 the Rio Grande sold it to the US Navy as one of the replacements for wood box cars destroyed in the monstrous July 17, 1944 explosion of ammunition ships and stores being loaded at the Port Chicago California naval transportation facility. It remained in use to transfer munitions between warehouses and ships from 1944 to 1971 when it was donated to the Western Railway museum along with another 36 foot box car. The museum repainted it into Rio Grande box car red. I was able to visit the train shed it was stored in and take a few phone camera snaps.
An article about the Rio Grande 36 foot box cars and modeling them using the Accurail 1400 series box cars in the Rio Grande Modeling and Historical Society Prospector quarterly magazine got me started. Grab irons were replaced with 24" grabs (Tichy) and new end beams made from U shape channel. The stirrup/sidebeam steps are Grandt Line Narrow gauge steps and may be too short for a standard gauge car, but they look right. The under frame was modified so the beams correctly align with the doors. It took a while but I located US Navy transfers from Clover house to match the car. Unfortunately they did not go on completely on the side of the car I am not showing. I am thinking about copying the Clover House transfers to decal paper to do a second car.
The cars were all Navy off white color when delivered to the WRM according to the slide I located on the WRM website. As far as I know they were in this color in 1948-54 which is my target period. The underside of 63383 is still an off white or very very light grey (and the K brake cylinder still lettered for a USN 1971 brake test.) I used spray can Tamiya White Primer to cover the boxcar red of the Accurail undecorated body and as the base color which covered completely after 2 coats. I then brushed an overcoat of Tamiya acrylic paint with 5 parts white mixed with 1 part light sky grey thinned with 1 part Tamiya acrylic thinner. I left it a bit streaky.
My research indicates the Navy non sea-going asset equipment numbering system (61-00202) dates from 1948.
I became very interested in these box cars and their story. My shunting yard used for testing models and pictures is in theory the SP Avon Contra Costa yard where the San Ramon branch left the San Joaquin line to go south. Avon yard is only 1 mile west of the Port Chicago/Concord Navel Weapons station interchange trackage. And I live 10 miles south in Walnut Creek where the July 17, 1944 explosion which completely destroyed two loading cargo ships and killed 332 people was heard. Although unlikely, I theorize the unloaded car was occasionally seen at Avon yard as a buffer car for switching explosive cargo to the Navy trackage.