Those cars came with low end sets, ....
here is the challenge, though, and is one of the main reasons i love Marx.
try finding a set of these (2071, 2071, 2072) in C7 condition.
Marx trains were made to be toys, mostly sold in department stores next to stuffed animals and baseball bats. even if there were high-end train stores in the 40's & 50's, Marx trains would probably not have been part of the inventory. Marx flat car loads are prized not for their inherent value, but because once the train got replaced by the next Christmas, the truck, tank & airplane were already on their way to filling other roles in the sandbox.
these passenger cars, like the silver frame cars, were given a less than top quality plating job which was easily scratched or worn off in the traditional grab locations. i wouldn't bet the farm on this, but i'd certainly wager a round of pints that there are more original Lionel Blue Comet sets in C7 condition than a trio of these NYC Marx cars in the same C7.
the OP car has one of the most common symptoms... no big damage, but a whole lot of little scratches/ marks. if you don't find these cars together, it's not very easy to put together a matched set.
cheers...gary