Zinsco electrical equipment is known to be hazardous for several reasons. There is a problem with the bus bar and breaker contact points arcing and overheating. Overheating the electrical contacts on breakers can destroy the integrity of this important safety item. Many reputably electricians won't service these anymore, and replacement is strongly recommended. They have been manufactured with aluminum bus bars as a clip on the breaker that make poor contact.
Arcing has been observed in where these breakers contact the bus. This can result in the overheating and incapacitation of the breakers. We observed these breakers have their cases blow out and leave soot on the inside of the enclosures. Note the extensive soot inside this panel and inside the cover, this is a sure sign of overheating and is an extreme hazard.
These panels were also in later years manufactured by Sylvania. This is the Zinsco design and has the same reputation. The Sylvania like the Zinsco had the blue and foil label inside and colorful red, blue and green breakers. With the same flawed breaker and bus bar connection design. These panels are ones that we recommend replacement.
We recommend that anyone with one of these panels have them replaced as soon as possible.