AC/DC adaptor for engine jumper (generator/battery) was left outside...?

[CapNSplooge]

Can I still use this adaptor? I left this adaptor for charging the engine jumper (battery with jumper cables) outside for a few days. It looks fine; it might have rained a little. It seems like the adaptor box (3"x3"x3" size) is completely sealed, the wire is fine, and the plug at the end looks fine. Anyway, I guess the safe thing to do is get a new one- probably will be expensive though. Thanks.

Class 2 Transformer. Model: HXT-13050, Input: 120VAC 60Hz, Output:13.5VDC 500mA, Efficiency Level: IV [Charger For DP600" label on wire]