Probably the best way to understand and get a feel for a 'normal' pound sign is to practice handwriting them, until you've got a sense of what comes naturally from the essential form and what is within normal variation.
As I learned it as a UK schoolkid (this is me thinking step-by-step about what I do when I do it without thinking about it, so may not be totally typical but should be close enough to be useful):
- Start at the top, curl it round it round like a back-to-front question mark
- Reach the bottom of the stem, go left a bit to assert a baseline then take the baseline out right to more-or-less match the top of the curl - this may or may not result in a small loop
- Take pen off paper and add a very small quick crossbar half way, crossing through the stem
Most of the flourishes and variation are within normal variation for how it is hand-drawn. Sometimes the
[reaches for typography textbook, fails to find relevant term] serif-like foot thing at the bottom left is a loop, sometimes the stem curves to meet it and sometimes it's a straight right angle because the pen goes out there when it reaches the bottom of the stem then doubles back on itself without leaving the page. The stroke width usually thins a bit here, as the pressure on the pen usually drops a bit - this bit is a common flourish rather than an essential feature.
The key essential thing here is that the bottom corner is a very sharp corner, in contrast with the curve at the top. The top curve of the stem must be unambiguously curvy and the crossbar must pass through the stem (not start at the stem) as this is what differentiates it from an
E. There are additional common optional features that are within the normal variation in handwriting that can be added to a typeface to make the difference between
E clearer, as necessary - the bottom left foot thing, a downward curl at the top right starting point, and a kink bringing the stem back in towards the centre like a backwards
There's sometimes a serif or a
[reaches for typography textbook, fails to find relevant term] bold blob thing at the top right because that's where pen initially meets paper, and there's sometimes a serif flick at the bottom right because that's where pen leaves paper. There's never normally an upward serif at the bottom left because the pen just turns there, it doesn't leave the page.
The crossbar is usually a thin perfectly straight line even if everything else is highly styled because it's a separate pen stroke - a quick even sidewards flick before moving on to the next character. Most of the variation in width is what would happen if that first pen stroke was done in a calligraphic way.