Local place to sell my Halon fire extinguishers?

[Brass]

DF - what would be a fair price among us hoodlum? Something that won't leave the buyer or the seller feel ripped off? It's super expensive stuff, and I don't want to get a bad rep in the trading post, if you know what I mean...

Cobalt - I think these cylinders are too old to recertify, and I have a feeling that transferring my Halon 1211 into new cylinders would be seriously expensive, perhaps hundreds of dollars. These fire services are accustomed to commercial accounts who are not very cost sensitive. I'll call around in the morning anyway, but I suspect that I'll get sticker shock in short order.