Hi Roland,
The holster is actually dated '23 and better suited for my 1906 or 1906 W+F lugers.
I am looking for an early dated M1900 Swiss holster...but that may take a while to find.
With the little bit of extra width of the M1900 dished toggles knobs, my M1900 luger will not fit easily into this '23 holster, especially the last inch of two of travel. I think the M1906 lugers with their flat, checkered toggle knobs are a bit more narrow than the M1900's.
Regarding the addition of the magazine pouch on top...since I assume this was an add-on at the descretion of the gun and holster owner...my guess is that you could see them added on any Swiss holster in this time frame. Just a WAG, though...
Regards,
Pete...