I'm going with "it's old". I've seen pictures of head lugs with the bearing races cast in, like yours on old frames possibly from around the 20s or 30s. I suspect there might be another part that slips in for the balls to run on. You may want to check back with the seller to see what he knows. Also, the chain stay treatment isn't a unicrown, it is a wishbone stay which dates back to at least 1900.