Leather workers finding old coins (7)

I believe the answer is:

tanners

I'm a little stuck... Click here to teach me more about this clue!

This might be a double definition.

'leather workers' is the first definition.
(I've seen this in another clue)

'old coins' is the second definition.
Although both the answer and definition are plural nouns, I cannot understand how one could define the other.

'finding' is the link.

Can you help me to learn more?

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