This DHBP is off VH 108603, an on-again, off-again project. On the back of the butt plate, the handwritten last three digits of the SN are still visible. I think a pencil was the tool of choice for that marking. Many parts carry the full SN or the last three digits, since hand fitting was required. So, a mix-up may not quite fit or function or a "missed" part during assembly would be obvious. This explains why it is good luck if you use a different numbered part on a project gun and it fits with no extra work required.
So.... if you take off the butt plate, you might still see the last three digits. If it matches the Trojan, that goes a long way to proving or disproving a factory DHBP on a Trojan. The odds of using a DHBP with the correct last three digits that didn't come from the factory with the gun would be small but an opportunity would exist every 1000th gun before or after a particular SN if that too had a DHBP. That seems wildly remote.
So, what's behind the butt plate????
Cheers,
Jack