Hi Guys, That definately looks like an older B&M 10" converter. Not a bad piece for it's time. It was made originally from a 10" Ford C-4 type core and looking at the blade angle on the pump cover, I would guess that it should be approx 3500 stall behind a mild big block and approx. 3000 stall behind a decent small block. Hope this helps you out a little.
PS - The weight is for an externally balanced 360 or a late 340 w/cast crank