Check the mag facts tacked to the top of the forum for more information on those first 30s produced by Colt.
As far as what are they worth...It's worth as much as someone will shell out in hard green for it! If I recall correctly (IIRC) the last time I saw some on the Equipment Exchange (EE) a fellow had some in near new or as new condition and he was asking $30 each?
What you do have is a fine magazine that is worth every penny for use, and if a guy is wanting it for a collection [puke] you should charge him twice as much as the guy who wants to use it.
My old man used to say, "Oh, you don't want to scratch that firearm/mag? Hang it on the wall...It will be just as useless to you tomorrow as it is today." In my humble opinion (IMHO), He's very wise.
I hope you don't mind me repeating myself with the full use of the sentence + the jibber-jabber but I noticed your new to the sight and I'm still figuring out what all the jargon means. Hope it proves helpful to you.
TIA.
Sly
By The Way (BTW) TIA was supposed to be your line, in means "Thanks In Advance". I just figured that out yesterday. It really threw me off because my brother dated a gal named Tia and I figured she must be getting around a lot. Laugh out loud! (LOL)