[The Philpott]

My own opinion...
Collectable? Yes.
Rare? probably.
Use it or put it in a glass case? Use it- with new batteries- (but not Duracells.) You could always get another analogue meter to back it up, for outside jobs or dirty jobs.

It is likely that a collector would pay good money for it (they are popular) but it would perhaps be better if you could use it, see if it needs any attention, and benefit from having what is an interesting link between analogue and digital technology..? When these meters are working, apparently they are very good.

Dave