As Rothhammer1 posted a link to my old doublegunshop post above, I repost a slightly updated version here:
The photo, posted here again, shows my M24 rifle and two scopes with Vienna style snap-on mounts, a Kahles, Vienna "Mignon 4x" on top, now on a M-S M1905, and a Kahles "Heliavier 4x" below. The Heliavier sits on top of my M1924 Mannlicher-Schoenauer in 30-06.

Here is another Heliavier on another Mannlicher Schoenauer:

and a third one (a Zeiss "Zielvier", but same dimensions):

Note: though the scopes are the same size and all three are mounted with the three-legged Vienna style snapper mounts on M1924 Mannlicher-Schoenauers, all three mounts differ in detail. These mounts were offered pre-WW2 by Steyr as a "factory option", but apparently they were handmade by outworkers/ gunsmithes outside the factory. Nothing is interchangeable. These mounts were all serial numbered to the rifles. There is no current source for these mounts. All you can do is to scrounge up such mounts and scope at gunshows or on ebay or egun and handfile the missing parts to fit the tops to your gun bases. The mounts are usually soldered to the scope tubes, sometimes even brazed, as I found out to my dismay. So you need someone able to completely dis-and reassemble these old scopes first. And, these Vienna Schn�ppermontagen are not the best mounts anyhow when it comes to stability and durability. Usually, windage adjustment can only be done by hammer and drift punch, slightly moving the front base in the desired direction. So a simpler approach is to remove the existing bases, store them for later collector purposes and fit modern bases into the existing cuts.