It appears to be an older Hi-Amp circuit breaker like this.
Since these came in various sizes I would certainly verify the exact amp rating before you replaced it. Too large and you could have a big fire problem. Too small and it will continue to reset.
Auto reset circuit breaker. Since you say that it had a 6 gauge wire hooked to one side and a 16 gauge wire to the other, it is probably not functional anymore. It may have been installed for a previous inverter or energy management system that is no longer being used. Certainly a 16 gauge wire cannot handle 135 amps and 6 gauge wire is only rated for around 60 amps.
I would either NOT replace it or verify with an electrical diagram for YOUR coach exactly what it was used for. If you are right about the gauge of the wires that are attached to it, it IS NOT 135 amps.
