What is this for kinda cap ?

[Ser-g]

Lets bring this threat up one more time.

Its been 4 years, and still with out a designation.

I have looked many times to the cap in and out side.
There is noting more to find than the already stated.

I have long time thought it would be of significance the writing inside.
It looks like there is a K.M.Z (or such) and 3/3 .
That makes me think what is the lettering a short for and this cap is 3 of 3 ?

I have seen one other for sale.
So it cant be a mishap or such.