Items found on a face, miners taking ages left inside (8)

I believe the answer is:

numerals

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'items found on a face' is the definition.
(Roman numerals on a clock face)

'miners taking ages left inside' is the wordplay.
'miners' becomes 'NUM' (National Union of Mineworkers).
'taking ages' becomes 'eras' (I've seen this in another clue. I am not sure about the 'taking' bit.).
'left' becomes 'L' (common abbreviation).
'inside' indicates putting letters inside.
'eras' enclosing 'l' is 'erals'.
'num'+'erals'='NUMERALS'

Can you help me to learn more?

(Another definition for numerals that I've seen is " Symbols for numbers".)

I've seen this clue in The Telegraph.

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