Question:

I know that on the 1975 – 1976 Colorado truck plate, GTM stands for gross ton mile. Do you have any more information on the plate?

Answer:

The Colorado GTM plates were for trucks with a gross vehicle weight over 6000 lbs. These plates were issued from 1975 until around 1990 when they were replaced by GVW (gross vehicle weight). LU-MH were allotted to Larimer County.