That's a very interesting find! While I don't specialize in overdates of the UK, I have quite a few others to recognize signs of digits underneath. I see something underneath the 8, and definitely underneath the 1. Often during this period, the date was added after the die was made using a smaller punch. If the date wasn't positioned correctly the first time, it was adjusted and most of the first impression was polished away. This might be what we're seeing here, where the vertical shaft of the 1 remains because it's the deepest part of the digit.

If the same date was punched a second time, it might not be listed as an overdate, but as a repunched date.
Edited by DVCollector
09/13/2009 12:43 pm