What year is this Yamaha DT with VIN number 1m2-106250 And how do you find out the year from this VIN?

Bike is a 1978 DT400E the first 3 digit letter number code and the first number of the serial number identifies the model and year. IM2 identifys the model as a 1977 or a 1978 DT400, the 1977 model serial number began with a 1M2-0 in 1978 they began 1M2-1.