And adding a quote from Italian Vintage Drums and Cymbals by Luca Luciano (who is a member here and might know more since I've only got the 1st edition of his book):
Lately Spizzichino has been hosted by a metallurgical company in Pescia and the cymbals, made entirely by his own hands were marked first as "Artisan cymbals by Roberto Spizzachino". The name Spizz has been sold, and today you can find inexpensive cymbals with that name which have nothing to do with Roberto.In collaboration with the company that hosted him, he also constructed elegant snares in maple plywood, planks, steel and copper with the name of the establishment GAM (from Gli Antichi Mestieri / The Old Crafts).His solo production includes sets with copper shells, stainless steel, zinc-coated steel, brass, sometimes chemically treated on the outside...
I've seen some non GAM snares (and whole drum sets) which have different lugs and have his signature engraved on them. So it sounds like there were two sorts of snares in production.
Two GAM snares are pictured at the bottom of p119 (where this quote is found). The photo on the right is just labelled GAM snares and it looks like the one in the OP including lugs, rims, strainer. The one in that PeralDrummers link looks the same as well. The one pictured on the left in the book is called Rullanti GAM and is polished and looks a more coppery color but seems to have the same rims, lugs, and strainer.
I believe that Luca is member hipercussion on VDF. You might want to contact him for more information.