My my, George. That's likely a rare piece you have there. It's possible it was a creation by a repair department assistant I've heard of named Roul Bloom. Stories have it that he was doing the "movie" guns for a while. Since yours appears that it might have his initials for a serial number, it might have been one of his personal guns. It's my understanding that his widow has sold a few of them.

You might want to share your inquiry with the Collector's group on the Yahoo site. Maybe they could supply more info.

...Deeton