An Inland Barrel does not make it an Inland Carbine. I'll bet you have a commercially made carbine with and Inland barrel and other USGI parts. That pretty much dispels the "bring back" and "Lunchbox" theories.

I’m curious as to how you determined it was an Inland carbine in the first place. While it is relatively easy to tell the differences between carbine manufacturers by the features of the receiver itself Reisch’s book doesn’t have any of the necessary info one would need to make the determination.