was based on an improved, 1962's single-stroke Leica M3 black paint model bearing S/N beyond 10599xx*
Other minor variations/features (esp. those earlier production units) may exist.
I have also provided a simple illustration of a typical double strokes, early Leica
M3 version at mid section for comparison (NOTE;- there are combination of other features
to confirm and/or verification purposes on version/model, even as minute as the design
of the camera strap eyelet on both sides (early DS M3 has triangular shape, later
models has rounded ears etc.). Please also take notice Leica offered Factory Conversion
Services such as double strokes to single stroke, addition of a viewfinder frame
pre-selector and even modified to accept Leicavit for auto film advance mechanism
etc. and there were even faked to make it rare kind of services by 3rd party technicians.
Hard to be a collectors today, so, traders with good experience as well as highly
rated trading credibility & a little extra premium may seem justified at times.
* Note: S/N for Leica M3:- 700000~1164865.
Collectors Guide, by