The symbol ℔ (image below) is an abbreviation of the roman term ‘libra pondo’ which translates to ‘pound weight’. However, this symbol was printed with a horizontal line across, so as to not confuse the lowercase L with a 1 (the number, one).
Another symbol that originated from and is used more commonly than ℔ first surfaced on twitter in August 2007. However this symbol quickly spread beyond twitter, and made its way into the Oxford English Dictionary in 2014.
what is the symbol I’m talking about?
p.s. The QoTDs run separate from the Winter League and are not scored on time so you can take a step back, relax and sip your cup of coffee while the mysterious owl stares at you.
Don Quizote 
Hashtag
Hashtag
hashtag (#)
the (#) hashtag or pound symbol
Hashtag
Hashtag
Hashtag #
#It is the hashtag
# (hashtag)
The hashtag
Hashtag
Hashtag #
#
Hashtag? Just a wild guess…
Hashtag or “pound” symbol (#)
Pound sign.
The hashtag
Hashtag
The “#” symbol !?
# (hashtag) for pound
@
hashtag #
Hashtag
Hashtag
You are correct! The symbol is Hashtag, also known as the pound symbol and is used after a number to mean “weight in pounds”.