Well, without any markings it could prove to be very difficult to ID the barrel. However, it was real common until the mid 80's, before anyone was making aftermarket parts and barrels,
to have the original barrels shortened. If it was shortend to 11.5" to mount the fake CAR style long FH the markings were probably on the end of the barrel that was cut off. Might want to also check to make sure it is a 11.5" barrel and does'nt have the slip over type FH. If it is the original barrel it should be a 1/7 twist chrome lined barrel. Now, all that said, I had a Oly Arms Car-15 in '88 with the 11.5" & long FH that had no markings on the barrel.