Case 580K year Serial number

I have a question regarding the serial number/vintage of my Case 580K Construction King.
There is a plate on the left side of the steering column which has the following information:

Product ID
580K
*1 741976

ROPS
*12201220*

These numbers do not seem to correspond to any of the numbers being thrown around on all of the related websites.
It seems there was a significant change where the serial numbers started to start with JJG but I cannot find any list that covers the apparent serial number on my machine.

Seems that the parts are before/after JJG so I need to know what I have.
Does anyone have any helpful information?

Thanks in advance.

Attached Images

 

Case 580K year Serial number