Originally Posted by John E
The only multispeed 1/8" cogsets I have seen were hybrid drive train adaptors for Sturmey Archer 3-speed epicyclic hubs, to give one 9 or 12 speeds. I used those with 1/8" chains and either 1/8" or 3/32" chainrings, which worked fine, as long as I had enough width in the rear derailleur cage. (Old Campagnolo Gran Sports, Cyclos, and Simplex TdFs worked fine.)
I have a four-speed block on my 1961 Raleigh Lenton Grand Prix, and it uses a 1/8" chain. But anything produced after the mid 60s would use a 3/32 chain, I'd imagine.
Neal