That gun is most certainly Italian. This design was built by many of the Italian makers: Beretta, Bernardelli, Siace, MI-VAL, and others. The examples from Bernardelli are the most common.
I have actually have a 12ga for sale now (pictured below) that is the same basic gun as the 16ga posted above.
http://www.gunbroker.com/Auction/ViewItem.aspx?Item=219169104
Here is a 20ga Bernardelli that I once had. Notice the similarities?
Bernardelli still builds hammerguns today using this same exact action design.
Adam
