A Puzzled Cranium
This one will make you think. But don't Overthink it!
It’s only easy once you know the secret. I hope I can count on you to keep it!
The original lock only had three digits but time, temperature and Atmospheric conditions had caused it to cease functioning.
You will notice a new four digit padlock on this geocache now.
So to keep it simple,
I will tell you the last digit is the same as the number of Teenage Mutant Ninja Turtles… I am not counting Sensei Splinter.
A big thanks to WVTim for the idea