Here's my undated "Patent" AW with 36 holes.
S-A mythology relates the undated Patent AW hubs were either made early, before the K hub production was ended, or assembled during the war when bomb fuse manufacture ran light.
I wish this hub could talk and tell me its history!
I think the second explanation is closer to the truth. The bikes I've found the undated hubs on, and the innards of those hubs, all looked to date to the early WWII era through just after the war (1940-48 based on the bikes I've worked on). There are a couple variations of undated hub imprints, one saying "Patent" and the other saying "Patent Pending". The "pending" one logically would be a touch older. In fact, I'm currently rebuilding a 1947 Schwinn Continental 3 speed with an undated "Patent" AW hub.