KTM 125 Barrel Identification

[Bill Campbell]

I now have two 125 barrels. One has EZ 54/1R and 5/4A on the side,base of the barrel and the number 1 stamped on the top of the top fin above the inlet port. The other has EZ 54/2R and 6/A on the side,base of the barrel and the number 2 stamped on the top fin. Can someone explain these numbers for me? Thanks Bill