Honestly I don't know. I was talking to a smith I know today and he asked me where he could find it. I do know it's an old one. He found the right side but that supplier did not have the left and could not get it
The recent manufacture ones I know are made in China, and parts are supposedly almost non existant, Double barrels made years ago were mostly made in Spain or Italy, and a lot of different variations, you should be able to find some markings under the forearm that might give you a clue as to where its made. I'm sure he knows about gunpartscorp if he's a smith, I've also found some odd gun parts on ebay from time to time.