we used to have this metal round cylinder-shaped box at work.

it had a removable lid with 2 slots in it and was meant as a kitty for the coffee-money
so that it wasn't always the one person purchasing filter-coffee for everybody else.

because we helped a lot of people with their stuff and did plenty of favours all round,
we got lots of bottles of wine & whisky, but some people just left us tips in the coffee-money-box.

so john wrote coffee tips on the lid.

only after John left the job we found underneath all the pennies his coffee tips.

they are the ones on the left.