Numbered roller rockers

[Red Rider]

Looking over the roller rockers for wear, they seem uniformly in ok shape. The roller itself can slide slightly along its axle, and you can see bits of the inner needle bearing. The roller surface is shiny, smooth, and free of defects. Then I noticed a number - 48. Each one had a number. Not in sequence, and not unique:

3, 10, 11, 13, 14, 36, 43, 44, 48, 51, 51, 51, 51, 52, 53, 55.

Anyone know what these numbers mean, and why they aren't in sequence, and there's 4 of a kind?

 

[DSMPT]

Could be wrong but IIRC I was told that those numbers are a production identification number/mold number.