Contax Zeiss Lens Serial Numbers

1. Zeiss Lens Camera
2. Zeiss Ikon Contax Serial Numbers

Zeiss Lens Camera

Zeiss Ikon Contax Serial Numbers

Evening, So I have just bought a 28mm F2 on ebay, Japanese seller and perfect feedback, bought from him before. Its a nearly new lens, MM, greed little number on the barrel, little black tab on the mount. But the serial starts 615XXXX. I have seen a few of the 28 F2's and the 135 F2's with early 61. Serial numbers on. Seems like a definite MM lens but I do remember reading that MM generally starts with mid 6's as the serials? Any experience? I know the 28mm F2 was only ever made as an MM lens in germany and would have had earlier serials (ie not 7's and 8's) but didnt think MM went that early?