It's quite a coincidence that you would mention having a 1926 Hohner Grand Prix. I've had one for a year that a friend gave me, and he said it was from the 20's. I didn't really know that was true until a couple days ago that it was that particular instrument, after scrutinizing the markings on the front. I had contacted Jim Pettijohn, who had offered to help me identify it. I was wondering about an alternate tuning, but decided to leave it as it.

My friend acquired it at a local accordion tech's shop here in north-central Wisconsin (Polka Country, USA...). It had some reeds replaced, but the bellows were/are good to go, in my opinion, anyway. He payed about $100 for it, all fixed up.

I agree, it really is a joy to play, and I understand your wanting to get it up to snuff. Jim cerainly knows his stuff, and not only has a passion for Cajun accordion, but also knows the ins-and outs of repair/tuning work.