Is this a PTC or a fuse?
Chances are very good it's a 250mA one-time fuse. I don't think anyone can say that resettable fuses NEVER look like that, but I can say that every fuse I've seen that looks like that is a one-time fuse, and most small SMT one-time fuses do look like that. Eg. these ones

Edit: I didn't notice the bel (manufacturer name) on the ends of these, as well as some other markings, until the photo was enlarged. Maybe OP's fuse has similar markings. Here is a datasheet for a fast-blow bel 0679L fuse which is similar.