The Fur Burglar!
Yes. Keith had a hybrid glued to slate from around the same time frame as yours, and when they first moved to Regne they sold quite a few LL’s (the yellow side) glued to slate. But it’s definitely not something that’s common.Not as noice as a Burton Series 0001, but, it'll do!
BTW David, have you ever come across a Les Lat glued to slate?