good as gold

Etymology
In the sense of high and enduring value, with literal origins in trade ( and ), where any given currency or commodity may be worth as much as or hyperbolically described as such.

Adjective

 * 1)  Of high and enduring value.
 * 2)  Very well-behaved (especially of a child); very  (especially of an adult).
 * 1)  Very well-behaved (especially of a child); very  (especially of an adult).

Translations

 * Finnish: kiltti kuin lammas
 * French:
 * German:
 * Polish: dobrze wychowany