I've seen those claims as well: "tested to industry standards." The claim is pure BS. Part of the problem us that there is NO way to effectively test a breaker.
Oh, there was once an ANSI standard that had something to do with testing breakers. The problem was, the standard only addressed certain aspects, and was quite specific in stating that it was NOT intended to be used ro check used or reconditioned breakers. Over at UL, it is necessary to destroy a number of breakers in the testing. After a breaker is 'listed,' quality control tests at the factory are complimented by on-going destructive tests.
Whether ETL is as relaible as UL is another story; considering the shennanigans that Chinese manufacturers seem to delight in, I suspect that there's a reason they are avoiding the UL follow-up testing.
It occurs to me that a currently available breaker costs only $8, while the Zinsco-type replacement costs ten times as much. Do, I think I will combine approaches: get a 'bargain' used Zinsco off the internet, and back-feed a breaker at the panel. That way, even if the obsolete breaker fails, I still have the panel protected.
