Which years had 100 or 120 mph speedometers?

I’ve got a 75 Scamp and it has a 100mph speedo. The 1975 parts book doesn’t list a 100 or a 120mph speedo so for sure by 75 it was only 100mph. Likely had something to do with Nixon signing a bill in 74 to help reduce fuel consumption?

Question now is if 100mph speedos were available before 1975 or was it only 120?