Actually that looks like about 90% of the mandolin banjos I've ever seen. Oviously this was made for the trade. Unless Jim Garber of someone else can ID it from that inlay on the headstock (and I've seen that inlay on numerous intruments)you don't have a good chance of really finding the maker. Take a mirror and see if there is anything on the top of the dowel stick. On rare occasion there is information stamped there.
If it plays well (as well as any mandolin banjo can be expected to play) and it sounds good (again, as good as any mandolin banjo sounds) just enjoy it. It wasn't built by Gibson, that's about all I can say for sure.
"bargain instruments are no bargains if you can't play them"