Steve I'll get more images up for everyone to see
I've had this one for something over ten years, and I haven't gotten into it to make it run - but I will.

My impression had always been that it's a Beringer, or heavily Beringer-influenced, or possibly the inspiration for the Beringer action.
There's no maker's name or mark. No proofs. There is what appears to be a serial number and there's a numerical mark for the barrels.

That opening assist feature, like many "patent" features, likely precedes (by the likely date of it's manufacture) any patent application.

There are some other interesting features.