Hi guys,
I saw a photo of the Swiss canvas frame bases Michael was talking about. They're an exact match for this base. Nice dig Michael!
I took the pintle/MG mount part out of the base to see what it looks like in comparison to Brian's. Brian's is nicely machined and has the qualities of a proper pintle, whereas this one is very crude. There aren't any markings I that I can find, and the shaft has "nubs" welded on for (I suspect) adding diameter to the shaft so it would fit better in the base.
I still wonder though if it was a real mount adapted for this base, or a home made jobber.
Thanks for your input guys!
Chuck