Part 1
In 1908 the German Army accepted DWM's Luger as its service pistol P-08. During its first three years of Military production contract, DWM delivered approximately 42,000 Lugers (Still, "Imperial Lugers"). Reasoning that DWM would not by itself be able to produce the number of pistols required by the military, and probably not wanting to be solely dependent on a commercial manufacturer, in January of 1909 the government appropriated money to start up P-08 production in the Prussian arms factory of Erfurt, in Thuringia.
Save for disputed examples dated 1910 (which may indicate a small pre-production "proof" run), the first Erfurt Lugers were delivered in 1911. It is estimated (Still, ibid) that 10,000 Lugers were delivered that year, all with no serial number suffix. These pistols were the P-08 pattern without holdopen or stock lug.
One noteworthy characteristic of Erfurt-manufactured Lugers is the presence of inspectors' marks on almost all of the small parts. These are small, upper-case Fraktur letters surmounted by a crown. According to the 1910 Instructions for marking the P-08, some 30 parts required stamping. This requirement was adhered to rigorously by the inspectors at the Erfurt plant, as opposed to the DWM factory where these parts were almost never stamped.
Presented here is 1911 Erfurt #7638, some three-quarters of the way through the 1911 production run. (The magazine is not matching and not Erfurt, and is in all ways ordinary, and so is not presented.)
The barrrel serial number and barrel gage display "halo", properly stamped through the blue. The witness mark appears perfect to my eyes.