This beautiful cameras quite hard to dig up information on. Heres some I found:
This is very rare version of M2. Only 875 units were produced for the U.S. Military during Vietnam War, which later became the M2-R designated for civilian use.
The valid serial # range is: 1163150-1163770 & 1164046-1164300. [this cameras serial matches the first batch]
The M2 KS-15(4) is considerably rarer -- five stars in the Leica guide as opposed to four for the M2-R.
In short: it is a M2 modified specially for the U.S. Military to have an M4 loading system, like the M2-R. Unlike the M2-R the top plate only shows M2 - I think there may be other differences but Im not a Leica collector, sorry!
Mine is in Exc+ condition. It has a few marks on the body as it has been used by me and (I believe) by previous owners. I bought it from one of Londons best camera shops last year who checked it over for rangefinder alignment etc. and gave me a years warranty on their work that I never had to use. The finder is very clear, the RF patch is contrasty, the wind-on crank is buttery smooth - it really is a treat to shoot, and Id keep it if I wasnt incapable of shooting with a meterless M.
Im asking $2200 for it: I think this is a fair price. Last year a worse condition camera sold for $2800 (japanese market), and the rather dubious one on ebay at the moment is listed at $3000.
Will ship insured worldwide, payment via Paypal please. Also please note: rewind crank and lens are not included in the sale! Thankyou.