From
http://faqlight.carpassion.info/hl-hid-bulbs.htm :
What does the P/N on Philips bulbs mean?
Legend:OEM=Original Manufacturer Equipmentaftermarked=sold as spare bulbs or manufacturer of kitBulb base: P32-d
85122: D2S. Color is bluer white with slight greenish tone.85122+: D2S CM (Plus). 5000K. Aftermarked only. Ment to pair up with used 85122. Released Q4, 2002.85122WX: D2S Ultinon. Aftermarked only. Released Dec 2001. Ultinons label on bulb were later relabled to " Philips BL-2 Non automotive use"85123: D2S. Color is bluer white with slight purple tone. Not officially on Philips product list. Nevertheless, it is found in some BMW OEM HID headlamps. Click here for a color comparison to 85122.85407: D1S. Integrated ignitor.85407+: D1S CM (Plus). Integrated ignitor. Aftermarked only. Ment to pair up with used 85407. Released Q4, 2002.85126: D2R.85126+: D2R CM (Plus). 5000K. Aftermarked only. Ment to pair up with used 85126. Released Q4, 2002.85126WX: D2R. Ultinon. Aftermarked only. Released Dec 2001.85408: D1R. Integrated ignitor.85408+: D1R CM (Plus). Integrated ignitor. Aftermarked only. Ment to pair up with used 85408. Released Q4, 2002.
"CM" means color match.There is a 4 letter date code following, which looks like this: L029, C024 etc. What they mean is probably not very useful unless you do warranty work for Philips.
It looks like the bulb of choice is the 85126(D2R) and not the 85122(D2S).