It's a single cavity nose pour 429421 with the pin in the base. Not very popular but since it's a nose pour it can't be cut with the 421 cherry. Add hysterical and semimental value and it could fetch a couple hundred or more. Not an expert, just shop.
There was a hollow point as well that was more popular.
There was a good deal of excitement when MP Molds brought out the #503 which is available in hollowpoint and I think in that first group buy also a hollowbase. I will have see if I can find it. You see in post #10 Miha offers a #503 but it's not clear to me that it's hollowbase like the wadcutter.