Its temple was very rich: The temple is evidently the one mentioned in 2Macc 1.13. This clause may be rendered “Its temple contained many rich [or, costly] things.”
Containing golden shields, breastplates, and weapons: Although it is not clear, the adjective golden presumably describes all the named items, not just the shields. These objects would have been plated with gold for decorative purposes. Gold is a very soft metal and would be nearly useless as defensive armor. Of the named items, only the Greek word for breastplates (see the comments on 1Macc 3.3) is an unambiguous term. The Greek word translated shields means broadly “coverings,” and is translated “helmets” in the Syriac and in one Latin manuscript. The Greek word rendered weapons is likewise vague, and often means “shields.” Goldstein is probably right in rendering the three terms as “helmets and breastplates and shields.” This makes all the objects pieces of defensive armor. It is hard to see why any offensive weapon actually intended for use would have been plated with gold. An adequate translation would be “shields and body armor.”
Left there by Alexander, the son of Philip, the Macedonian king who first reigned over the Greeks: The book began with a reference to Alexander and his father Philip; see the comments on 1.1.
Good News Bible offers a fairly good model for this verse, but it can be divided into smaller units:
• The temple in that city was very rich [or, contained many costly things]. King Alexander had left gold shields, helmets, and other armor there. (Alexander was the son of King Philip of Macedon, and he was the first king [or, high chief] to rule the Greeks [or, the Greek Empire.])
• The temple in that city was full of many costly things: gold-plated shields, helmets, and other armor that King Alexander had left there. (Alexander was … Greek Empire.)
Quoted with permission from Bullard, Roger A. and Hatton, Howard A. A Handbook on 1-2 Maccabees. (UBS Helps for Translators). New York: UBS, 2011. For this and other handbooks for translators see here.