Corndog
That same plane your asking about is selling on e-Bay right now. No bids yet. It looks just about the same plane as a Stanley #4 smoother plane. Nothing special there but might be special to you because it was gran pa's. Sharpen it up and hang onto it. Corrugated soles aren't the best though on a hand plane. Supposed to lessen friction when using but so then does a little wax on the sole. I have a whole cupboard of handplanes but most are Stanley or Veritas planes. Surprised ,you being a guitar maker, that you don't have any of them small instruement planes. You must use a file or rasp a lot? Good Luck
Mitch