Hi Edelweiss, and welcome!
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Gorgeous!
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To me, it looks as if it could be a circa 1930s 15/4 piano accordion, possibly made by one the excellent Italian Soprani families of accordion makers.
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The rattling noise is likely caused either by a reed and it's mount (reed plate) having come away from its proper location (reed block) due to the wax used to fix it in place having become friable due to ageing and having let go, OR a reed tongue having broken off, and either item having fallen into the pleats of the bellows.
Do not try to force the bellows shut as you may simply push the sharpish metal item through the material of the bellows, causing a hole!
There's nothing else quite like it on the net .
It has several unusual features:
•Exceedingly small size.
•A piano accordion with only 4 basses (the usual minimum being 8).
Are the basses the same on push and pull?
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•Slot-headed screws instead of bellows pins (sometimes found in old boxes from the 1920s & 1930s)
•Apparently, no metal bellows corners
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.
Does it come with a box?
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Quite a novelty!
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This little instrument could be worth repairing as they are quite useable by a variety of entertainers ( e.g., street artists and circus performers), or you could try to sell it "as is".
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There appear to be a couple of musical instrument repairers located around about Boise : it may be worth taking it to them for a consultation?
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Very interesting: thanks for sharing!
Good luck with it!
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