Welcome to the forum and the ranks of the makers marked confused.
I agree the dating to 1759/60 London but would question the identification of the makers mark to John Pollock . Grimwade gives two marks for him, nr 1572 (roman capitals in a vertically cusped punch) and nr 1596 (script in a very unusual heart shaped punch). Neither match your mark. Neither do they appear to match anything else in Grimwade !
Certainly the will of John Pollock,Goldsmith of Beltone Street In Westminster was proved at PCC on 22 November 1755 which sounds like the Grimwade John Pollock of Belton Street ,Long Acre.
So this guy was dead by end of 1755 and I think the pot is unlikely on these grounds to be by him
So I think we have another silversmith whose mark appears on your pot.
But who ?
My only guess is that this is a man in the lost small worker register of 1738 to 1758. Often silversmiths registered as small workers and went on to large work etc without registering another mark .
I will add it to the Lost Marks file !