Dating oscar schmidt auto harp datingsway com
The best ones and the ones people look for are the made in USA ones.About 1983 they switched to Korea and sometime in the 90's China. (Unfortunately, I have sold them all.) You should really check out Bryan Bowers. They are customizable as far as what bars (chords) the players wish to include or exclude. And those were the ones with a gazillion buttons too.They have a single string per note, so don't sound as full, but are more flexible in terms of available keys.
page from the Autoharp Store website gives a pretty good overview of the OS models.
If they need restrung there are extra set still available but they are expensive, about 60 dollars a set. Fortunately the strings last a long time because they are not fingered so even if you buy a USA made one from the 70's the strings are likely to be OK.
If they need work new felts, springs, and other parts are still available, and the parts from the old ones are compatible with the new ones.
If you're looking for fiddle tune playing, a diatonic model in G and D would meet most of your needs.
"Chromatic" Autoharps have up to 21 chords (extruded aluminum chord bars can be made very thin, so more can be crammed on to the top of the instrument), and can play in most common "folk" keys.