Hello again 22250Rem:
Thanks for the additional information and pictures. Unfortunately, I don't have much more to add. There are no marks on your pistol that would tie it to any particular unit. The German military officially abandoned unit marks in 1916, but some really officious units continued to mark their equipment after it was no longer required. Let me explain that I'm not an expert. What I know about German military marks comes from the books by Joachim Gortz and Albrecht Wacher, and Jeff Noll. With that and a lifetime of hands-on curosity, I might be able to offer a little insight into the marks on the right side of what is sometimes called the "fork housing". They are, as you mentioned, "proof and acceptance marks," although there is really no "proof mark" in the formal traditional sense of the terms, but rather the proofing process was part of the inspection process and designated by the inspection marks. In the last picture on the far right in your post there is a series of 5 different marks. The first marks in this photo (viewing them from left to right) are really two marks -- one above the other. The one on top is small crown over the letters RC. Known as the "RC und der 'Stern' Stemple," this is the mark of the "Revision Commission" which means that this pistol did NOT pass all the inspections originally, was submitted to this "commission" which inspected the pistol again and give its approval that it fulfilled all of the contract satisfactorily. This is not an "acceptance mark," it means that it passed inspection.... finally. The mark immediately below it is a capital letter in Fraktur script that is the first letter of the last name of one of the inspectors at Erfurt during the period your pistol was produced. The next two marks are similarily the initials of the last name of two other inspectors at Erfurt. These people were the Prussian acceptance officials and represented the interests of the government. The crown above each of these initials is important in that the crown was the symbol of national sovereignty and indicated that this pistol had fulfilled the specifications of the contract to the government's satisfaction. It was during this evaluation process performed by these individuals that it was "proof" tested. However, by putting their initial on the pistol, it meant they were also testifying that it meet the contract in terms of materials, workmanship, quality, completeness, functionality and accuracy, with different individuals conducting different parts of this list of tests. Here is an example of how the process worked: The first initial under the crown generally indicated that the breech metal hardening specifications and standards were met. The next letter under the crown indicated that an inspector found that it functioned well enough to go forward to loading a shelll and shooting. The last stamp, the small eagle, often called a Reichsadler" means that the pistol has been shot and accepted by the military inspector at the factory. And the last initial under a crown means that it was inspected again after shooting. Somewhere along the line of that process, your pistol failed and was diverted to the Revisions Commission, which reevaluated it and made a decision to send it on to the next step or not. The RC put its stamp on it, so they accepted it and it was sent to the military for distribution to the units. The unit would then inspect the pistol again and either accept it or send it back for more work. There was such a shortage of pistols, however, there seems to have been very few rejected at the unit level. Forgive me if I've made this all boring. One last point, the serial number involves both the number and that small letter under the numbers. It indicates that your pistols was the 5187th luger manufactured in the "d" or 4th series of 9999 lugers made at Erfurt in 1916. Unfortunately, to the best of my knowledge, there is no definitive list of when that would have been in 1916, but my best guess is that it would have been in the first 3 or 4 months of they year or earlier. But.... once again, nothing is certain. For example, evidently there were no lugers maufactured at Erfurt in 1915, and no explanation for why or when manufacturing of lugers resumed in 1916. Hope this has help shed some light without being too boring. Thanks again for posting.