XJ600 rim letter markings

I just bought another rim for my XJ600, everything's the same except these two letters. The original is a T and the new one's a G. Does anyone know what they mean? Thanks in advance for the help

 

Isn't the other marking different too?

 

I see 9|1 and 1|6

 

Yea, I forgot to mention that. The letter in the box and the numbers on each of the 3 alloy supports are different, but they are both J 18XMT3.50 DOT and R-61(whatever that means)

 

The "T" is probably a mold indicator (multiple molds for the wheel casting; which one did this casting come out of of? is useful for quality control and defect analysis purposes). The 1/6 (or 9/1, if in the southern hemisphere) may be a production date code.......so between the two codes, you could tell WHEN it was made and in WHICH mold was used........all the info that anyone could ask for when chasing production problems.....

 

Thanks Chacal