The numbers you are asking about are either serial numbers or batch/lot numbers, mine is MK7526. I would think that in either case the higher the letters/numbers the later in production.
There are difference between the originals, mine shown below, and the Coker reproductions. Note the smooth transition from the sidewall to the tread, reproductions have ribs. Also there are differences in the position and width of the red lines. The model type is different, this one is a "Super Safety 800 - XP".
Pic 1: The whole wheel.
Pic 2: Model type
pic 3: The opposite side where the serial number is located. Note the original Style Steel Wheel rivets.
Jim