The card failed. . .
Here's the 14 boxcar. The last picture shows it with the dark green 820. The 820 was coated with linseed oil by Al Levin to stop the paint flaking so it has a glossy finish.
The story on the boxcar is the Harmony Creamer company bought 24 cars from Lionel. Then the creamory mounted tanks inside, and put decals on the cars. This is from a late 1950s TCA quarterly article based on records from the creamory. The creamory did not modify four of the cars.
This could be one of the unmodified cars from the creamory, it could be an extra car made by Lionel to insure they had enough cars to fill the order, or could be something else entirely. No way to tell now.
When I attended Joe Algozinni's recent Zoom session, they were discussing cars Lionel made as specials, and a subgroup of specials made from unassembled parts. The Parker Hanefin 6464 car was an example shown. A PH distributor bought plain boxcars and added decals to them. This 14 boxcar is the oldest example I know of from within the unassembled specials subgroup.
An aside here: The TCA desert division in 1996 bought parts for a motorized unit from Lionel and then lettered them for preconvention specials. Paul gave me one of the shipping cartons that held the parts a few months ago.