This very clean 300mm f/6.3 Komura Commerical is in an older-style Copal 3S (marked only "Copal No. 3") shutter, with a 10-blade iris and non-equal spacing between the marked stops. There are no obvious problems with the glass and the exterior is in good condition with only minor marks of usage save for a nick in the rear cell housing - in the photos I aligned the aperture-setting lever with where the nick is. The shutter operates correctly and repeatably although the slow speeds sound a bit slow. It comes with a Rodenstock front cap and a mounting flange, as seems to be common for Copal 3S shutters (why??). Also included is a metal Komura lens shade. Filter size is 72mm.
Info about Komura Commercial lenses is scant and they don't appear in the one Komura document I've ever found online. This is a Tessar, not a Plasmat, so the 345-350mm image circle at f/22, similar to the Tessar-based 300mm Fujinon-L and 300mm Schneider Xenar, will cover 8x10 with a bit of movement.
Don't confuse this with the more common 300mm f/6.3 Komura in Copal 1, a telephoto (probably) intended for 4x5 use.
My asking price of $295 includes insured US shipping and PayPal G&S fees and shipped to your PayPal-verified address. International buyers - contact me to talk about shipping options. Note that I will not undervalue this on customs forms.