A (new?) twist on plural 's

[David Bowie]

At the Ruby's Inn general store (a terribly overpriced grocery store and
trinket shop just outside the main entrance to Bryce Canyon National Park in
Utah) yesterday, I saw the following sign over a doorway:

     Employees' only

I figure plural non-possessive s' (as opposed to plural 's) has probably been
witnessed elsewhere and discussed on the list already, but I don't remember
such a discussion and couldn't find one from a quick search in the archives,
so I figured I'd post it in case it hasn't appeared previously.

David Bowie                                         http://pmpkn.net/lx
    Jeanne's Two Laws of Chocolate: If there is no chocolate in the
    house, there is too little; some must be purchased. If there is
    chocolate in the house, there is too much; it must be consumed.