Does anyone out there have scaled drawings of the 870 Mk1 bayonet adapter? Secondly does anyone know what grade of steel was used to make these?

I work for a small metals service center and know several guys in the sheet metal and machining business. If I had proper dimensions I think that I could get a replica made. I have already had a duckbill choke made for a Ithaca 37, now have to get it heat treated and the permamently attached to a 37, so I feel like I could get the sheet work down as well, but only with proper dimensions.