This is a true story - I know, because I was there!

In the UK, with the introduction of the two pound coin, it was feared that the characteristics of the coin changed during its life.

Therefore, a certain coin mech manufacturer issued a load of its employees with two pound coins to simply keep in their pockets with their loose change - and the coins were measured from time-to-time to check for any changes.
Of course, the coins had to be signed for at the start of the trial, and signed back in at the end!

(The two pound coin was the first bi-metal coin in the UK.)