I bought two Polulu 30:1 1000rpm micro motors a few years back and cannot find what voltage version they were. Any markings or tests I can do to figure out the max voltage of the motors without trying it and possibly frying them?
Since you bought those motors a few years ago, they are probably 6V units since we did not start selling 12V version until July of 2016. You could double check this by running them at 6V and measuring their no-load speed. One method for measuring the speed of a motor like that is discussed in this forum post.