Please do not consider that was a pound sign. A handwritten pound sign likely needed two horizontal lines through it. To me, it is a Capital L that has been written and then excluded from the official registration.
My reasoning:
I am old enough to have been taught to write a pound sign as a capital L wirh two strokes through the downstroke. I am young enough to remember how to divide pounds, shillings and pence by pounds, shillings and pence, and to appreciate a Guinea was a pound plus commission.
JM in NSW Australia just after 1 a.m.