The “commercial at” has notoriously had a massive shot in the arm with the development of e-mail addresses. No doubt selected because it was the least used symbol on the keyboard, it may now be the most popular. It used to hide out in price listings, where it would show up as “2 lbs butter @ 11d = 1/10”. (For the puzzled: 2 pounds of butter at 11 pence a pound = 22 pence, which is 1 shilling and ten pence.)

The erudite blog, Typefounder, written by James Mosely, has an extensive history of @, dating from October 6, 2013.

#, which we call hash-tag now, is another symbol plucked from relative obscurity (by Twitter). We use it in the book business to mean basis weight.