Buckstix, though the rifle is still a Haenel model 1900, not the improved M1909, it was proofed after April1, 1912, when the Suhl proofhouse made the change from gauge numbers, here it would be 67.49, to millimeters, here 10.5mm, for the bore= land (NOT the groove or bullet!) diameter of the barrel. So it was completed for sale between 1912 and 1914, when Haenel switched to military parts production. The CROWN-crown/N proofmarks show that it was proofed using the "special 4000 atm proof powder” for a service load containing 3.2 gramm = 49.4 grain of the fast burning military rifle powder and a steel jacketed bullet, weight not given, as usual.
I agree with Lancaster: this 3.2g load seems to point to the 10.75x57 as an original chambering, but I am not sure. All three cartridges, x57, x63 and x68 existed in 1912 and Dixon even mentions a 10.75x61, listed in the DWM casebook about 1906 as “for Haenel”. If the rifle was rechambered, it was done outside the German proof law, as there is no crown/R or eagle/I reproof mark visible. The 10.75x68 marking may be a later clarification as well.
The other markings, letters and numbers, are unidentified, factory internal quality marks, serving then to identify the craftsman who perhaps made a blunder.
That “seesaw” front sight was apparently a Haenel special order feature. I have seen this sight on several Haenel marked rifles, not only on M1900s and 1909s, but on M88 ones too.