[John Sabato]

perhaps this excerpt from Gerard Henrotin's DWM Lugers E-book will pin this down this frame...

[quote]Naval Lugers (P04 & P06, 9mm para.)
Even though the German Military Board closely followed the Luger technical evolution, it was not until 1904 that the pistol was officially adopted as a service sidearm. By that year, the Marine Admiralty decided to order a specific version better suited to its requirements than the standard model. The pistol was henceforth known as the model P04 or Naval Luger.
It differs from the standard model by its barrel length (150 mm), the adaptation of a variable rear sight with a two-graduation scale (100 - 200 m) on the rear toggle link, and the presence of a stock lug to accommodate a specific detachable wood stock. This latter was made of a simple wood board, provided with four slots to let leather straps pass through to fasten a holster. A specific metal disk was screwed on the middle left face of the board and sometimes unit markings were struck onto it.
The frame was of long type and the main spring was the old flat one. The breechblock was a new model with a three-piece extractor marked on the left side with the word "GELADEN" (loaded). The toggle knobs were checkered at right angles. The wooden magazine bottom was designed with concentric moldings.
The first order of the Imperial German Admiralty "Reichs-Marine-Amt" was placed on December 12, 1904. The order was for 8,000, 1904 Lugers, and they were to be delivered by the DWM in the fiscal years 1905/06. When no deliveries had been made by January 17, 1906, the "Reichs-Marine-Amt" gave the DWM delivery deadlines for 2,500 pistols until end of March 1906, for 2,400 in April, and for 3,100 by the end of May 1906. These pistols had of the lastest technical improvements, such as a new long frame equipped with a coil main spring, a breechblock fitted with the new extractor and no toggle safety. The old fat straight barrel was replaced by a tapered one. A second batch of 8,000 pistols was ordered on fiscal year 1906 (ending on March 31, 1907)

- Source : J. G�¶rtz.
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Stock Lug, Coil mainspring, Long Frame, No Toggle Safety, Serial number in the 9XXX range? looks like that = P06 Frame to me based on this information...and probably reworked for the holdopen and short barrel post war...