I have overhauled a Chemnitzter. If you find any broken reeds Harmonikas can replace them at €25 each. You'll have to send them the plates. Tuning a Chem is fun because it doesn’t have reed blocks you can put on a tuning table. But I was able to tune the plates flat on the tuning table and then tweak the tuning with then in situ, but you need to be able to lift the end on and off from the bellows. It’s a bit tricky. All the levers etc are held together with animal glue so repadding can be done but it’s also more tricky than a melodeon. Finally, it’s probably tuned in octaves, which is challenging to get bang on the money. Tune one reed to ref pitch, then the octave to that reed, until their is zero or near as dammit tremolo. ...and, having just sorted out a PA where the previous tuner clearly had no concept of the reed set or profile - apart from rough tuning the plate flat on the tuning table, you also need to voice the reeds to make sure they speak with the merest breath of air.