AYA Cosmos 12 Gauge 30" Break-Action Shotgun

The configuration you described refers to the AYA Cosmos, a highly regarded, vintage break-action single-barrel 12-gauge shotgun. Manufactured by the elite Spanish gunmaker Aguirre y Aranzabal (AYA) in Eibar, Spain, the Cosmos was built primarily during the mid-to-late 20th century (heavily throughout the 1960s and 1970s).