what does "of the first water" mean?

[johnxyy]

English Language Proficiency Tests, Advanced Level

ESL/EFL Test #408 "Water Idioms", question 9

The jewels in that showcase are clearly of the first water -- means: ..........

(a) of high value
(b) of high quality
(c) of high reputation
(d) of high density

English Language Proficiency Tests, Advanced Level

ESL/EFL Test #408 "Water Idioms", answer 9

The jewels in that showcase are clearly of the first water -- means: of high quality.

Correct answer: (b) of high quality

Your answer was: correct
_________________________

what does "of the first water" mean?

thx
johnxyy

[Mister Micawber]

.
of high quality. ETYMOLOGY: Probably translation of Arabic m', water, water luster.
.
_________________
Native English teacher at Mister Micawber's