Hi Steve. They were pretty common on the Bacon and Day, and most 'upper -end' Gretsch banjos. I doubt they got used much by the pros who could actually afford those instruments though ('cause learnin' to play quietly is one of the skills needed to BE a pro), also they tended to put the banjo out of tune. Just press you finger into the underside of the head (under the bridge,) and you'll see what I mean.

Cheers

Rick