Howdy
Sounds like you got a good deal. Many of the Detonics guns were built on Essex frames. There are only so many companies that build frames and everyone buys from them and then finishes them. If you buy a frame that is 80% done(no rails cut) then you don't need a serial number. Your gun sounds like a a kit that was put together right. I really dont think you have a real Detonics but if you are not looking for a collector gun and it works then you got reall good deal! The original slide, rug and mags are probably worth the amount that you paid for gun! Anyway you cut it you probably got a good deal!
L8r
Conley Janssen
USMC 87-93
Check the Detonics group on Yahoo and the DetonicsUSA web sight