First to the markings: The circled "little rooster" (="Haehnel" in German dialect), surrounded by CGH, was the trademark of the C.G.Haenel company, Bahnhofstr. 16, Suhl. Haenel made many M88 military carbines and rifles , not only for the German army, but for export also. They used their actions to build most of the M88 sporters too. So these Haenel sporters are not converted surplus military rifles, just as the Remington 30 rifles are not ex-military P14 or M17 Enfields.
156.14 (.,/ interchangeable) is a gauge number like we still use on shotguns, lead balls to a British pound. As these numbers were taken over from Britain, 156.14 stands for a bore/land (not groove /bullet!) diameter between .310" and .320" (141.95).My own Haenel M1900 in 8x57I is marked 118.35 = .300" - .310". These gauge numbers were used by the Suhl proofhouse from 1893 to 1912, replaced by mm figures in increments of .1 mm.
The CROWN + crown/N proofmarks stand for Nitro proof using the special "4000 atm proof powder". This proof was used from 1894 to about 1923.
The rifle was proofed for the M88 8x57I sevice load of 2.75 g = 42.4gr GewehrBlaettchenpulver = (military-)rifle flake powder behind the 227 gr Stahlmantelgeschoss = steel jacket bullet.
"Star" was a high quality barrel steel by the Boehler steel works, Austria.
The other small letters are worker's stamps, factory internal quality control marks, unidentifyable today.
The scope is a very early Voigtlaender, Brunswick, "Skopar", one of the very first rifle scopes, offered from 1895 to aout 1905.
These early sing mounts were overly complicated and not recoil and wear resistant. By 1910 they had disappeared from the market again.
The rifle was retailed by Jacob Sackreuter, Friedenstr.3, Frankfurt on Main, founded 1830, last mentioned at the time of WW1. My own 8x57I Haenel M1900 was retailed by Sackreuter also. It is mounted with a Voigtlaender "Skopar D", a long eye relief version.