References:
1. Tom Heller: Luger Forum ditto, 8 July 2003 (see above)
2. Ron Wood: Luger Forum 7 July 2003 (see above)
3. Walter, John: â??The Luger Bookâ? (1951), pg 231. This reference is WRONG, and it is this erroneous information about the M2 safety marking that started this thread. It is interesting to note that the Portuguese Luger was so little known at this time that Harry Jones in his â??Luger Variationsâ? (1957) did not have pictures of any Portuguese Luger, and in the section â??Lugers Not Shown In The Catalogâ? lists â??1909 PORTUGUESE (also 1934) with SEGURACA [sic] by thumb leverâ? and â??PORTUGUESE: Reportedly with GNR over the chamberâ?. Even by the 4th printing of the book in 1975, this information had not been updated.
4. Kenyon, Charles: â??Lugers at Randomâ? (1969), pgs 134-135 (M2), pgs 254-255 (GNR)
5. Walter, John: â??Lugerâ? (1977), pg 182
6. Bender, Eugene: â??Luger Holsters and Accessories of the 20th Centuryâ? (1992), pgs 434-435
7. Walter, John: â??The Luger Storyâ? (1997), pg 124 (M2), pg 210 (GNR)
I am sure there are some other references, but this reading list should get you started.