Kurt,

At one point in the mid-to-late sixties, Schwinn ran out of its stock of Nervex lugs. Nervex lugs had always been a pain to get right, requiring lots of work to get a good frame, so Schwinn switch to Prugnat lugs in the late sixties. It was not a popular change with customers, so they went back to Nervex lugs.

The lugs on the eBay bike don't look like the Prugnats I'm familiar with; maybe they're from a third lug vendor.