I just remembered a fascinating post on the history of the number sign which I thought everyone would appreciate:

https://widespacer.blogspot.com/2015/10/the-sign-of-number.html

Also, two other good posts from the same blog:

https://widespacer.blogspot.com/2016/03/the-lost-key-of-qwerty.html

https://widespacer.blogspot.com/2015/11/the-hidden-secrets-of-qwerty.html