Barrel date on STD PRO from CMP

I just received a STD PRO carbine from CMP; s/n 2168xx, with Underwood barrel dated 10 - 44. Ruth/Duff reference indicates that s/n receiver was produced in the January - March 1944 time frame. How could it have such a later barrel, by which time only Inland and Winchester were still making carbines? I recall that Underwood was allowed to continue making spare barrels for some time after all the other manufacturers contracts were terminated about April 1944. Was this 10 - 44 barrel likely a replacement for a worn/damaged Underwood barrel with early '44 date?

Absolutely!

I have a Standard Products receiver (2048XXX) from 10/43 with an Underwood barrel dated 10/44 (obvious replacement). Its the definition of a mix-master with not one major part of the carbine dates/matches the receiver... but that underwood barrel measures .5 on a gauge. Its a definite shooter not a collector but I couldn't ask for one in better condition!