Wheel date code. Tell me if I am reading this correctly??

Wheel date code.
Had a little time this afternoon and was looking at the steel wheels that were on my 69 dart. Here is what I found on all 4 wheels: M with a 9 under it, to the right 6, then to the right of the valve stem a 3, then a 5.5. I think the date code is telling me they are 6/3/69 5.5 wide. Am I reading that right?
Joe