A THREE-WAY Toggle Switch is the means to select from 3.1 to 2.05 or 1.3 on my A2000 - its on a tang in the unpopulated Zorro section.
This was the usual switching method for the Kickboard from Unitech Electronics.
I actually have OS' 1.3, 2.05, 3.1, and 3.5 but 1.3 can't run on the 060.
There is also a switch to change the CHIP to a lower value but I've never used it.
° Providing instructions, for the next user, is a good practise.
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The A1 -- Its a small step for a computer - a BIG step for AmigaKind!