On the right hand grill, that centerpiece of what looks a bit like a harp, is something that is often used by early Paolo Soprani accordions. That and the register mechanism looks very similar to my old (also non-playing) Paolo Soprani Italia. The treble keys... either never played in the sun or in smoke filled rooms, are way whiter than what normally one sees, I would suggest that those are later replacements.
Jim is right about the abalone, this is a member of the clam or shellfish family. The inside of the abalone is often perl-ish or iridescent... just like your accordion shows. Red California abalone are some of the most prized in the world due to their iridescence and colours.
For someone that really likes this accordion, it would be one that is worthy of being completely refurbished and used, one does not come across these beauties very often.
Value? That is unfortunately another story. Accordions don't have much of a value on the open market today... only worth what someone would offer for it. Greatest value would be to be lovingly used and played.