Coolant reservoir..."new old stock"

[rah rah 986]

I just purchased a coolant reservoir for my '98 Boxster. I purchased a Porsche model with the most updated number of 99610614708. The tank arrived in a plastic bag with a paper label indicating that part number. What has me puzzled...suspicious, is that the part itself is embossed with a different part number: 99610604710. This number is almost the same as the number that is on the original part that I have removed. The original tank has the number 99610604704. While I am convinced that the part sent to me is a Porsche factory product, I don't think that it is current. I have heard that there have been many updates on this part over the years. When I google the part number imprinted on the new tank, the only results I get are for used, second hand tanks. And, the number does not produce any results when I search it at any of the Porsche suppliers that I have checked with. Does anybody have an idea of what is going on here? Is it normal to get a part wearing a different number than the part number that it was sold under?