The symbol of the Lead Pencil Club is a yellow Number 2 pencil with the text NOT SO FAST.
I have learned that American Number 2 is equivalent to Australian HB. The Australian ( in reality British ) system is that pencils with soft dark graphite are called Black - B. The more black are modified with a number - 2B, 4B, 6B, etc. Pencils with hard graphite are designated H, these make a fainter line. They are also graded with harder - and fainter pencils modified with a number - 2H, 4H, etc.
HB pencils are supposedly the happy medium between H and B. They are the most popular grade. You can buy they in packs of a hundred.
In 1971 - in primary school - I had moved to a new grade and - disgarding my slate - I was using HB pencil and paper. The teacher disgusted at the grubby marks on my writing pads called my mother in and said that I was to use 4H pencils. This would prevent me smearing graphite over the page. I did all my school right through to university with 4H pencils.
Recently re-looking at pencils - in my attempt to not use plastic biros - I find that I prefer 4B sharpered to a fine point. This gives a dark legible line.