Hi Mike,
This topic came up recently in a discussion over on Jan Still's Gun Boards as well :
http://luger.gunboards.com/topic.asp?TOPIC_ID=11321
A member, named Armin from Germany, indicated he had seen lots of M1906's and even M1900's with un-numbered TD levers and the 2-digit stamping on the trigger side plate upside-down (i.e. top of numbers pointing towards the side of the Luger instead of away from the side of the Luger).
BTW...regarding the P-release date stamping on Swiss Lugers; you will see them in 3 possible configurations :
1. Letter/numbers stamped and then the gun reblued by the Swiss at time of gun release. This will result with "bluing" down in the stampings of the P-date.
2. Letter/number stamped and showing a "halo" effect. This has two possiblities :
a. Halo appears on an original finished gun.
b. Halo appears on a previously refinished gun.
In this case # b, one would need to look for other signs of a refinish to determine if the halo is on an original finished gun or on a arsenal refinished piece.
As the Lugers in CH were in service many years and issued to possibly several, sequential soldiers, the Luger may have been arsenal reworked 1-2 times or more before finally receiving its P-release stamp which would display halo if the gun was in great condition at its time of release from Military use and did not require a refinish.