Doug,
Congratulations again on a very early Luger. The Crown/B Crown/U Crown/G proof marks were used on the early commercial Lugers.
The front dimension of the receiver / breech block and extractor are quite different in the early Lugers. These were revised in the 1900/06 and 1906 specifications. Therefore the firing pin components must be the ones for your specific model.
This one should be in the 7.65 x 21 mm Luger Parabellum (.30 Luger) caliber. You should find that a standard No.2 pencil will just fit into the barrel. Here's info on the ammo:
http://en.wikipedia.org/wiki/7.65x21mm_Parabellum
This model Luger also used a "S" shaped leaf style rather than coiled recoil spring. If you have not already done, consider carefully removing the grip panels to check the condition of the recoil spring.
You have a very early Luger and it is collectible. It would probably be wise to not try and fire it since you could risk breaking parts, especially since there may be corrosion that is not visible.
Ask Tom Heller about a firing pin and extractor. Also post on this website in the Wanted section.
Collectors would recommend that you not modify the Luger in any way. That said, it may be possible for a restorer to fix some of the corrosion issues if that is important to you.
Cheers!
Marc
__________________

Igitur si vis pacem, para bellum -
- Therefore if you want peace, prepare for war.