Would be very nice if I could see the coins in a coffer made of gems, just
like you can see the equipment inside chests made of gems.

How many gumballs are in the Jar?

If you don't get my point, it's hard to guess how many of a mass object are
inside of a jar and especially a see through coffer would be hard to count.
With the chests it easy to point out a few items.

++ Dutois

Well then, how do you see the number of coins when you open the coffer? Assume
that the coins are sorted in a logical manner, that the coffer magically
tallies them, or that there are little hand-drawn labels attached to the piles
of coins that say what each pile is worth. Either way you should be able to
see that if the coffer is see-through!