Selectro Locking Hub question

[jocko]

Is there an easy way to tell the vintage of a set of selectro hubs? Weren't there some that used to be silver and then some that used to be black (as pictured) - or were the silver ones just well-used black ones with the paint worn off...? Did they go out of production at some point? Seems the only "new" locking hubs manufactured nowadays are warn 9072s, so kinda curious. Interested in a set of selector hubs - guy is advertising them as "NOS" which is odd because they were not factory items (at least on chevs) - I think he really just meant vintage (and unused). Anyway, tomayto, tomahto. Most members lean toward the selectros over the warn premiums. My warns are worn way out and all pitted/banged up - so considering replacements. Would prefer something period over brand new and have located a nice set of selectros, just can't tell how old they are. Thanks all!