Looks like it might be the same base, used perhaps both for stock bending with one set of clamps on it, and for another use with a different set of clamps. The copper covered "spillway" just at the wrist of the stock would certainly make me think of pouring hot oil on the stock. Perhaps in it's "second" configuration it is used for reattaching a loose lug to the barrels. I don't see enough sideways clamping in the picture to make me think it would straighten the barrels, and bending both together would be tough, so, that's my next guess. A jig to reattach forend lugs.
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