I'm unsure what you mean, the only weapon codes i know that exist are the Beta Flaming skins, Gold Retro and the Liquid green skins which are now on the marketplace.
All other skins are on the marketplace only, when you buy them, a code is not generated so you will only find the beta skins, or liquid green, infected omen skin packs.
Please correct me if i'm wrong but i am certain that i am correct.