[The Philpott]

I think there should be felt in the lid (there should certainly have been some around the sides of the base)

The original cell type had a screw terminal which engaged with the sprung fork, the other terminal was a wire en-bloc with the cell, which joined to the brass post at the corner of the battery compartment. This cell is obsolete so you are stuck with modifying the meter for a C or D cell (easily done)- but you might want to investigate the siezed pots before bothering! The meter might have been somewhere wet for a while causing the bakelite to swell. Completely siezed pots are uncommon - it may have had a hard life.

Dave