Charlie looks to have the best guess for those numbers.  They would appear to be some kind of mold identification numbers.  Considering the number of rockers required for a years worth of production, there are no telling how many hundreds of molds were required in which to keep up with the number of engines going out the door.

Lorena, Texas (South of Waco)

I understand what your saying/ but each side of rocker has a different # and no 2 rockers have the same #/ maybe Ted tell us what the # are for

The original FoMoCo rocker arms are iron castings, Kansas.  Having worked in a green sand iron foundry at one time, I suspect that the numbers you're referring to indicate the particular set of molds used to make the sand mold for the individual rocker you're looking at.  Sometimes numbers are also used on sets of castings to indicate other things like work shift, date, or the molding machine making the part.

Hope this helps. 


NoShortcuts
a.k.a. Charlie Brown
near Syracuse, New York

also still looking for 1 ecg rocker to buy  I try john does sell just 1 

Can any one tell me what the 3 digit # stand for that are on both size of rocker were the adj screw goes through/ out of 16 ecg rockers none have the same #