Oh yeah, Gruhn's the guy, but....tell ya what, why don't you send 'em over to me, let me try them, and I'll give you a good estimate!

That ol' Gretsch will fetch quite a bunch, and most old Martins, if they are decently playable are off-scale, value- wise, especially a 1930!  OUCH.   But as db hinted, musical quality will vary, no matter what the vintage. 

I bought a Martin D-35 double herringbone in 1985 from a dumb appearing, but as it turns out, very enterprising young redneck (scary redneck, bib overalls, chew, pistol on the table, replete with the trappings of redneckdom), in Kannapolis NC.  He had a room full of them, that he had secured from people who just didn't know what they had and sold it to him for absurdly low prices.  Or...he took them at gunpoint (maybe the latter).   Anyhooo..my guitar was modestly priced, but the only other guitar in the room that sounded better was a 1947 thing that I could not afford.  Not every old Martin has that sound, they are very inconsistent, but when they're great, they're amazing.  Good luck.   Tell me what happens.

G

P.S. It may interest you to know, that Martin is about the only large guitar company that does NOT do endorsements.  In other words, they don't give some hot picker a "free" Martin and let him or her go around the country endorsing Martin guitars.   Many other commercial guitar makers do follow this practice.  And they're still headquartered in Nazareth, PA.  I still don't know where the hell that is.