It isnt a tag. It is the stamped serial engine # on the block.
Basically you look up the # on the block to determine the year. This isnt perfectly definative as more of an approximation. John Deere made certain block numbers on particular years. So if you provided the block #, we could tell you the year. Alas I can only presume your block # is in the approximate place as my 60. It will be a machined flat spot with stamped letters near the flatbelt pulley. A model A owner will be able to describe it better than I can.