Just bought a Koken late 19th century with all parts, metal needs plated and the leather replaced paid 1600 Canadian. Here's some links about Koken chairs and...
well if you go on the website where you got it from you can type it in and see :P good luck!:)
around 1964..that's the date that i found on mine. Is it related to the motor cycle brand ? Thanx K.N
It sounds like a Koken Model 505 early 1920's.