In order to complete my front brakes, I need to get some rotors that would fit my calipers. As I don't know what they are from (and there are no part numbers on them), I headed down to PorscheTech in Bedminster, Bristol. The guys down there were very helpful and identified the calipers as belonging to a 944S2 or 968. With this information I could determine their part numbers, and what rotors they need. The caliper part numbers are 951 351 421 03 and 951 351 421 03, and the rotors are 951 351 041 02. These rotors are 298x28 in size, which sounds right for the calipers.

All I need to get now are the hubs.