Barks' story???

[Arie Fachrisal]

Hi,
i was wandering and i remembered a story that i read long ago when i was at
age 7-10?, and i remembered this one story which i liked very much. i don't
know the title or the artist. Please help.
The story DD hired by U$ to clean up the money bin/coins, i forget which
one, sorry. Instead of paying usual payment, U$ somehow let DD to search for
a coin or two he likes and he can keep it. DD found out that most coins in
the bin are very rare and have high prices. He went back and forth from the
money bin to a "coin collector shop"?, so finally U$ found out about it by
spying DD from the window. The ending- i totally forget.

Merry Christmas and Happy New Year everybody.
Arie Fachrisal