In 1924 the 3250 had a headlight added, so that makes them easy to spot. In 1925 some or most of the 3250 used the newer stamping that had indentations for the brass plates even though they never had brass plates. The numbers and lettering on these locos was simply stamped into the indentation for the plate..

Above chocolate brown, below dark green both are probably 1925 with the headlight and the number stamped under the vents.

The salmon colored 3250 above is probably from 1925 notice the number is NOT stamped under the ventilators and the 'MOTOR' designation.

Definitely 1925 with the brass plate indentations and the lack of engine numbers under the ventalators.