I might be in the market for a blank/cap-firing MP40, for the purposes of WWII reenacting, but have never looked nor learned much about them...yet. In doing a little research now, and also reading Cerwyns post, so it sounds like some more pictures and clarifications are in order to confirm if the one you have is machined such that it can fire caps/blanks?
Have you had the chance to get some pics of the things cerwyn asked about? (I am located in WA state, so if there is some way to conclusively prove it *is* a firing model...you might just have a buyer here, relatively close by to you)
Thanks,
Lute