EXIDE MANCHEX auto battery (?) plastic sign (?) panel

Another thing I came across somewhere years ago, that I've also never really known anything about.

+/- 6" in either dimension, it's an opaque gray plastic panel with "EXIDE MANCHESTER" printed onto one side. One little chip outta its lower edge, as it was when I found it.

I think "EXIDE MANCHESTER" is a name related to auto batteries...maybe this was once part of some kind of store display sign or something...??