I'll have to research that a bit.

Offhand, I'd guess that as Stoeger didn't list them among their options on the 'prewar' models while claiming to be the "sole importer" of MS to the US since the late 1920s, that few if any M1903 through M1910 MS were shipped to the United States with military sights. The M1924 and other offerings based on its longer action (oft referred to as 'M1925' these days), which Stoeger referred to as 'High Velocity', had the "British style three leaf sight".

That says nothing, however, of production for domestic (European) markets and as such sights were being fitted by Steyr to the 'Greek' Y1903 and its variants through the years, and as evidenced by the 1935 Steyr Catalog, they were available as ordered options.

Perhaps Kuduae may have insight here?

I now find myself questioning my previous assertion that Louis' peep sight is modified or altered.

I wonder, given the early production of his M1905, if this could be an original early variant.

The peep sight shown in the 1912 Westley Richards ad and in the images of MS that I have posted differ from the peep on Louis' stutzen.

Notice the slide adjustment and notches on the upright portion of the WR peep that is consistent with the MS images I had posted and the peep on my own 1922 dated M1910 Takedown Model:

Typical pre - WW2 MS folding peep

Westley Richards, 1912 advert

Louis' sight:

The 'special folding peep sight' on Loiis' early M1905 stutzen seems to be of a somewhat different configuration than the others. Now I'll have to research to see if I can find M1900 MS with the 'special folding peep sight' to compare.