That is an interesting action and forend iron, or shoe, as Winchester call them. The action appears to have been made into a flat side, the reinforcing arrow panels appear to have been file off, Winchester did offer a flat side ation even before the M21 came out as a Custom Grade only. The action appears to have the ejector trip rods protruding from the front of the knuckle, but the iron has not been fitted for the ejector mechanism, although the iron appears to be an ejector iron; the iron is wider at the rear where the ejector hammers etc, would be fitted. No holes have been drilled for those parts, but a pair of rough extractors are included. Some of the extractor gun forends probably came this way.
Barrels are available for M21, some on the secondary market, and of course, Galazan can fit a set. In that the action frame is already a flat side, it has even more appeal.
I wish I could make the Engravers Guild show this year but it is not in the cards for me. I'd love a chance at that action!