Just before the last mag ban, I bought a bunch of magazines from Forrest Co. They have steel bodies and if you google them they get a bad rap on AR15.
This said, they are pre-ban. Can I sell them to people in states that only accept pre-ban mags? What are they worth?
Thanks for your input.

Yes

Sell them where legal to do so.

Can someone explain this idea a little better for an old fart who doesn't pay attention to a lot of these ban issues? I live in a free state (Virginia) and have around six older 30-round magazines I used to run in my M16A2. I don't use them, kept them in case I had to protect the neighborhood from the chicoms. Now I have pmags to run in my Colt and Ruger AR's and could sell them according to this post? They are used and no name brands like Cooper and Adventure but work just fine. So those poor California folk can buy these as pre-ban and use em?

No, they are not legal for Subjects of the republic of Californiastan.
The only State I am aware of that Pre-Ban means anything anymore regarding magazines is Massachusetts.

I thing if disassembled, shipped separate as parts.  Maybe the law changed.

Illegal in CA for over 3 years.

Edit to add more information on CA regarding standard capacity magazines.
CA banned purchase/future import of pre 94 standard capacity magazines in 2000, they allowed their Subjects to keep already owned Pre-Ban magazines with a Grandfather clause.
"Parts kits/repair kits" (disassembled standard capacity magazines) were legal for CA Subjects, they could own new magazines as long as they were not assembled/used in CA.
CA passed a law that does away with the 2000 Grandfather clause for Pre-Ban standard capacity magazines, "Parts kits/repair kits" making any magazine over 10 rounds illegal.

Yup, pretty much anything involving selling, shipping, receiving buying, etc. for parts is a misdemeanor, anything involving assembling mags or assembled mags is felony. General speaking of course, CA gun laws are a spider web so complex to screws people over on purpose

How do they know if someone has a grandfathered magazine or if they purchased it more recently?

Got a dated receipt?

If you were 18 or older in 2000 and resided in the state since then, they wouldn't know.