Dave Conception, Bat with 2 knobs?

[GoTigers]

Anyone run across one of these? I'd love to get one in the collection. This picture is from Sports Illustrated's Book of Baseball. It says the bat is from 1982, and it is a H&B. I thought maybe it is something Conception added to his bat, but it looks to be from the factory that way. The caption says "double knob bat". This is up there with a bottle bat, or mushroom knob. Sorry for the picture, it's from my phone.