[TJH]

Yes, as others have stated, it is an auto reset circuit breaker. Someone stole my battery about 6 weeks ago and disconnected the battery by just cutting the cables. I had to install new cables - one of which was attached to one of these circuit breakers. (I didn't know what they were until I went to a RV parts shop and inquired.) The cable had corrosion fused to the breaker stud, so I ended up destroying and had to install new ones. I found out:
1) Some are resettable, some are auto reset. The ones on our trailer were auto reset.
2) There were two on our trailer - and they are different values protecting different portions of the trailer.
3) To make reasseble more reliable, I take pictures of everything with my phone as I dissassemble and reinstall in reverse.

Learning something new every day owning a trailer.

To prevent or hinder future thieves, I fabbed up and welded a lockable "cage" to the battery frame.