I don't believe there was an actual Workbench 1.1. I thought it just started from version 1.2. Anything before that it was simply called Workbench and it wasn't until WB 1.2 was released that it was referred to as Workbench 1.1 or 1.0. The same way the Amiga 1000 was simply called "Amiga" and the 1000 was added later. Is this correct?
Edit: OK my mistake. There was 1.0 and 1.1 was just bug fixes.