I found it!

Exceeding chuffedness rules.
:¬)
When Ah waz a lad....
Mother/Mam had a "Fat pot". I guess it was Mother's and Mam inherited it. I haven't the faintest idea of its age, except "older than me".
It holds 2.5pints to the lip; where the design suggests there may have been a lid, but not in my time.
I can't remember it ever being less than 1/2 full of fat/dripping or whatever the current meat/bacon yielded.
I can't, hand on heart, say we used no fat; but sufficiently little as to render the Fat Pot superfluous.
I hadn't set eyes on it for so long I'd become sure it had been swiped out of the garden.
It came to light in the greenhouse when I started to clear around, prior to re-situating the bench.