Peterson426

I did take off the other side and there was a logo of a bird (eagle maybe) on top of a concertina with the words EINGETRAGENE SCHUTLZMARKE. Is anyone familiar with this logo?

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Hello all, My grandfather recently passed away and we found an old concertina in his things when we were cleaning. I know absolutely nothing about antique instruments, so I'm turning to you. There are 28 buttons on the side with the air valve, and 24 on the other. There are no exterior markings aside from a "made in germany" stamp and a plate that says "concertina" I opened it up and it looks very well made. I also found a stamp on the inside that says "4 18 29" I was wondering if that could be the date. Any information (maker, date, value, etc) you could give me would be extremely appreciated. This concertina is in great shape, if it is from 1929, it appears to been very lightly played and everything is in perfect condition. Thanks