[Milsurplus] Yep, 'F' cells

[CL in NC]

Lantern batteries should have 'F'' cells in them. I have used these in things like battle lanterns to simulate those old large 'A' batteries.  I have a battery operated beacon monitor receiver that took an 'F' cell for the filament, but was never able to find one except inside the lantern battery.  At some point, they must have been an option to buy individually.  They last a bit longer than a 'D' cell, and if you cut them apart, you can easily solder to the spots that were prepped at the factory for solder as some have aluminum cases.

Charlie, W4MEC in NC