Ask HN: What @ sign was used for before the internet?

Clicked through expecting to learn something new, but instead unearthed an old memory - thanks OP!!

When I was about 7 I used to help my dad in his shop. He had a fairly basic till (this was the 80's), which he would let me punch the numbers into. One day, someone brought 10 £1 items to the counter. I remember typing £1 repeatedly when my dad stopped me and showed me what the @ key on the till was for.

My mind was blown for about 6 months before learning I could just type £10 instead.

You can find in Wikipedia: https://en.wikipedia.org/wiki/At_sign

AIUI it was often used in shorthand in commercial transactions in order books like "12 widgets @ $10"