I'm holding a Schurter switch/breaker "T12 221 15A" in my hand. http://www.schurterinc.com/pdf/english/typ_t12-211.pdf (Scroll to page 5 for drawings). These are popular in European boats.

In a day or two I can post some of the Blue Seas part numbers, similar product and direct replacement.

Basically you push the button all the way in and it pops out for "switch off", push again and it's on. If the breaker pops you push it in again to reset.