Although it is not stated in this kit, I believe that these boxes are for holding 120mm tank ammunition. The photo above is from Goffy Model, and shows what this accessory set will look like when painted. Below are scans of the unpainted parts.

Included in the set are eight closed boxes, plus four boxes with open lids are provided, each box holding two shell tubes. The woodgrain detail on the boxes is excellent, and with the exception of only a couple of tiny pinprick holes in the resin, the casting is superb.

Thank you very much to Goffy Model for the providing the review item.