I remember seeing one at the hardware store back in the early 90s (drilled/tapped but reg rear site). The only ones I had seen in the "rags" came with the scope base, so I didn't buy it and got a 6 7/8 blued target instead... oops
If it's the one I saw on auction (GunBroker maybe), I thought of the two hole; three hole discussion when I saw it. Wondered who would buy it.................