Zinsco Breaker Panels
Zinsco electric breakers and panels are common, but the quality of the components used to build the panels and breakers are substandard. This brand of panel has had numerous failures, resulting in electrical fires. Much of the potential damage and problems with these panels is hidden from a visual inspection. For this reason most home inspectors recommend replacing these panels when found during a home inspection.
The link below contains detailed information about this type of panel and other panels with known defects. http://www.inspectapedia.com/electric/Zinsco.html
A burned and over-heater breaker at the connection to the bus bar. This type of damage is not visible during a home inspection which is why a licensed electrician should be retained to further investigate the breakers and panel for damage or the panel should be replaced.