[22shot]

Like several guys have pointed out; you have a "reproduction" BP Pistol.
I doubt if it was a "kit".
It was mfg. in Japan for Ultra-Hi. It is a copy of the British Tower pistol; On the lock plate it should have a "crown" over letters G R impressed between the hammer and frizzen; the letters S A R behind the hammer. The brass butt insured that the wood would't split when it was used as a club; after fireing your one and only shot.
This is just an educated guess; but it may have been made by Miroku; a top Japanese gunmaker. (I have a caplock .45 pistol; Ultra-HI; Miroku: Japan; and I've fired it. The workmanship is top notch.)
The presense of "proof" marks indicates your pistol is intended to be fully functional; it looks unfired.
As posted; it is worth at least $75 but not more than $200.

Collector value is in the eye of the beholder.