Forerunner of the pound sign (5)

I believe the answer is:

libra

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This could be a double definition.

'forerunner of the pound' is the first definition.
'libra' can be an answer for 'pound' (I've seen this before). I'm unsure of the 'forerunner of the' bit.

'sign' is the second definition.
(sign of the zodiac)

Can you help me to learn more?

(Other definitions for libra that I've seen before include "Constellation near Virgo" , "Zodiacal sign" , "Scales star sign" , "Person born under Scales sign" , "Zodiac sign of the scales" .)

I've seen this clue in The Daily Express.

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