Re. 3 over 7:
Not sure to be honest.
Even though worn, your coin shows evidence of having been struck from very tired dies. Might it be yet another case of chipping/cud?*
Look at how obvious the overstrike is on Colin Cooke's coin, both digits are clear.
Note also the horizontal bar of the 7 is in line with that of the 3. On your coin what may be an underlying horizontal bar is lower, and sticking out slightly on the right.
*(Chipping Cud, isn't that one of those places where the entitled hold their kitchen suppers? )