Do the third and fourth digit of the year look identical? Nah, 1971. By the way, what you have is the French version of the coin (country name "Belgique"); the Dutch version would say "België" instead ... Christian
JFTR, here are images of a piece dated 1971 and of one from 1977. That extra diagonal line after the last digit (in your image) confused me a little, but I don't think it is actually an error coin ... Christian