Zeithain (not far from Leipzig and Dresden - Saxony) was a former Imperial training ground, after the German Army (Reichsheer) was reconstituted (November 1918-December 1918 it essentially dissolved itself) these training grounds, especially in the east (facing Poland), were increasingly used to train the "Black Reichswehr", which essentially were paramilitary organizations and local militia types, to support the German Army (Reichsheer) in an emergency.
Zeithain was one such training ground near the eastern frontier, though I have never seen it specifically mentioned in books, most of the more active training grounds (engaged in training the Black Reichswehr) were along the German-Polish frontier. However it was one of the earlier HZa reconstituted and listed in most documents on the subject, so this activity probably pre-dates its actual "official" status. Little is known about this early period, 1919-1927, very secret and illegal at the time.
What is known is that Zeithain was a old training grounds, these grounds were extensively used to train because they were large, isolated and rarely if ever inspected. This was especially important in Prussia because the Prussian government was hostile (far left) to any military activity, because they felt the far right (military, aristocracy, any one of the old order - "nazis" were never-ever "far right" in ideology, the "far right" thought they could use them and build upon the nationalism appeal they had among the masses, as Groerner once stated "harness the masses with nationalism"... most of the old order ridiculed the nazis and rightfully so, as Georg Escherich once called them, nazis are "Nationalistic Bolsheviks", not men of the right.) was more of a threat than the Poles.
Secondly, Zeithain was a known HZa when they were officially reconstituted, - technically the ordnance shops operated illegally, they were not allowed under the peace treaty/diktat, though it was never pushed by the IAMCC as everyone knew the German response, - they would deny they existed, rename them and move them if necessary (as they did with every complaint). Officially three HZa existed early on, one at each Reichsheer HQ, Berlin/Spandau, Cassel/Kassel and a smaller operation in isolated Königsberg. It stands to reason that these reconstituted HZa had an earlier life, but little is known of its operations beside these few surviving rifles.
The rifles, they were made 1924-1928, the vast majority on leftover Spandau marked receivers, but a number of others are known, leftover Simson, Amberg and Suhl makes are known, especially early on. 1927 dated is most common, probably because this was when the pressure was most lax on this type of activity. The IAMCC was out, and these rifles stopped in 1928 because secrecy was less important after 1927. Basically illegal rifle making was practically impossible 1919-1923, between the chaos, the madness, the lack of structure, and later the scrutiny after the IAMCC came (strongest up until 1925) into being all made rifle production a very bad business to engage in. Very few rifles seem to have been made in 1925, probably due to the Ruhr crisis (France's and Belgium's effort to make sure the republic in Germany would fail), but by August 1925 things seem to have settle in and most rifles were made in 1926-1927, lingering into 1928.
The eagle/11 was one of several waffenamts used to inspect/accept the rifles.
These rifles are fairly common in lower grades, the vast majority are heavily used and abused, rifles with any original parts are rare. They are exceedingly rare in upper grades, - matching and original, especially with the original stocks. Only a handful have any matching parts, only a couple with their original stocks. While one of these in original matching condition would be as rare as an Simson 1924 or 1926 in like condition, many more were made, they just have a dismal survival rate in upper grades. While they are rarely seen nice, it is likely their prices would be soft compared to a Simson 98b, for one, fewer know much about them, secondly these were made as G98's so far as can be said. The only surviving rifles with stocks are all G98 configuration and would appeal to a smaller clientele...
The subject rifle was probably not worth tackling, unless it was a German conversion. Most aren't when found shortened. Would have been nice to get the data off the rifle though, - see if i had it documented already.