Thanks for posting the pictures, Sandy. Easy to see how it would not be difficult to read either one as 12,500. Perhaps the correct solution is to insure that the ' / ' is a well defined one, almost exagerated, and that it goes higher and lower than the edition size. If this were done there should be no potential to mis-read it.

The images show the flag much larger than real life and it isn't difficult to read it wrong. Shrink it down to life size and it would be even more difficult.