Determining a weatherproof padlock

I need a weatherproof padlock for my garden gate. I was given a Masterlock padlock with key by a friend and it has a blue plastic runner along the bottom on an otherwise metallic steel skin. Absent the packaging, how can I tell if this is a weatherproof lock or not? I don’t want it to get rusted shut on my gate.

Are there any model numbers stamped on it anywhere? Absent that, I don’t see any way, short of a field test, to determine if the lock will rust or not. What you can do is spray it thoroughly with WD-40 every few months. WD-40 is excellent at repelling the moisture that leads to rust (trivia: the WD stands for Water Displacer). Use it sparingly; you don’t need to soak it with the stuff–a thin coat is sufficient.

Sounds like a plain ol’ lock there. It’s probably weather resistant, so it won’t turn into a lump of rust after the first heavy fog, but weatherproof locks are pretty obviously so with their full plastic casings. And for about ten bucks, why not just go get one that you know isn’t going to rust shut?