First I must say I am by no means an expert on the 5500 (or any Rolex watches for that matter
) just trying to find common threads to help understand your dial.
I did not fin a match to your dial but I did fin a 3.3 mil serial (5500 - 1002 case back 1520 movement ) that has a close resemblance but as it is not the same not conclusive.
The key difference seems to be the lack of Tritium on the dial. I have seen a few that have T swiss made T or like the example below - T swiss T - so that is all I could remark.
I think further investigation may help understand your unique dial. Just maybe a later dial non tritium.
Bill