Coffer
Easton's Dictionary
The receptacle or small box placed beside the ark by the Philistines, in which they deposited the golden mice and the emerods as their trespass-offering (1 Sam. 6:8, 11, 15).
Smith's Dictionary
(argaz), a movable box hanging from the side of a cart. (1 Samuel 6:8,11,15) The word is found nowhere else.