I don't think they are Gehmann, but the only manual 10 mt changers I'm aware of are available on the internet from www.Frankonia.de in Germany, I don't think they are good value at over £100, when you can get good quality electric changers from Spieth at around £250 each direct and also from Germany, if you would like more details please e mail me.
Robin
Walther KK500 Alutec expert special - Barnard .223 "wilde" in a Walther KK500 Alutec stock, mmm...tasty!! - Keppeler 6 mmBR with Walther grip and wood! I may be a Walther-phile?