As a general rule, things stamped "Schwinn" were made by Schwinn. In their heyday they had a huge factory and, like Raleigh, they made everything on the bike. When they started having parts outsourced, they had them stamped "Schwinn Approved" such as the hubs and pedals made by Maillard, the brakes made by Weinmann, etc. I have read that some of the parts with a hard to read cursive "Schminn" were also out-sourced, but I'm not convinced. I would assume the cottered cranks were made by Schwinn. The one on my 1940 New World, pictured above, took 1/2" pedals.
I'm trying to remember who it was who told me the cranks were outsourced and brit. I feel like it was one of the Schwinns, but we're going back 20+ years and my memory is a tenuous thing.