This is an American Zettler 40A Miniature Power Relay. Its part number is AZ2120.
• 40 Amp switching capability
• DC coils to 120 VDC
• Life expectancy to 10 million operations
• High dielectric strength version available
• Class B insulation standard
• Class F (155°C) version available
• Versatility of both PC and “Trace Saver” quick-connectterminals on contacts offered on the AZ2120 version