Good Luck! It really helps the parts guy get you the correct part the 1st time if he has all the information you can give him. Because the bikes we ride are not new, many things could have been changed over the past 20+ years. Many European companies introduced new stuff when they got it, which was sometimes in the middle of a production run and not just on their new model.
Here are some examples of where you can find your bike ID.

Honda CR 125

Honda CR 125

Villiers Motor