The context will supply the key to know whether we have to choose here the meaning Jewish (adjective) or the meaning Jews (noun).
Remarking that word number 25 and word number 26 are within a single quote mark gives us an important clue: that היהודים is not an adjective that qualifies noun מטבעות, but a noun of itself.
Then the group would mean coins of the Jews.
There is here the risk to translate the group as Jewish coins or the Jewish coins.
This would be a mistake.
If you wonder why would it be a mistake: because the meaning The Jewish coins would require word number 25 to take the article: המטבעות היהודים
So we get the right translation: the Jews' coins or the coins of the Jews.
Certainly, from a practical viewpoint these two translations would be the same thing. But not so from a strict grammar viewpoint.
We find this noun nearly 50 times in the Bible: look at 2Ki 16:6.