David,
Imperial Military Lugers of WWI were numbered from 1 at the beginning of each year. At every 10,000 guns the number series was started over again at 1, with a letter suffix added, progressing through the alphabet until the next year. This practice was followed by both DWM and Erfurt.
Mauser P-08 began production at serial# 1 with the K date in 1934, and simply progressed through the number-suffix irrespective of year. Mauser cycled through the complete alphabet three times, ending in the n suffix block in 1942.
Complete serial number tables can be found in Jan Still's "Imperial Lugers" and "Third Reich Lugers", respectively.
Commercial serial numbering began with 1 in 1901, and continued to the 92,000 range in 1921. In that year DWM converted to numbering in the military style (four digits followed by a letter), beginning with the letter suffix i. The commercial serial range is separate from military production, the numbers are not intermixed.
--Dwight
--Dwight