Hi Johan, There were two different versions of the Ocean 500: one complete titan and one with yellow gold bezel. The titan is ref. 3503-001, the one with gold bezel ref.3503-002. I have no explanation for 11103. Kind regards, Adrian, (alwaysiwc).
As an IWC & PD factory authorized service center for more than 35 years here's an official answer to your question.
Since Porsche Design sold a wide variety of products, including timepieces first made by Orfina and later by IWC, they implemented their own product numbers and one for each variation similar to a SKU which identifies the product within the company's inventory database.
Thus, with your IWC Ocean 500 ref. 3503, PD assigned their corresponding number 1110/3 which is the all titanium model. The tag you have is most likely the original tag.
Tnx Jack for your help ! Good to learn new things and nice to know that everything is correct now when the watch is out for sale ! Best Regards / Johan