What's the difference between crownpiece and headstall?

Crownpiece

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Definition:

• (n.) A piece or part which passes over the head, as in a bridle.
• (n.) A coin [In sense (b) properly crown piece.] See Crown, 19.

Example Sentences:

Headstall

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Definition:

• (n.) That part of a bridle or halter which encompasses the head.

Example Sentences: