With serialnumber 57550 the gun is made ca 1963!!
See link.
By the serial number.
The age of your shotgun is determined by the serial number that was assigned to it.if you wish to include this number in the form of a question we will be able to age your shotgun for you?
That is impossible to determine without knowing the manufacturer and model of the shotgun.
Blue Book of Gun Values
Una Merkel died on January 2, 1986 at the age of 82.
By the serial number
70-100 years.
Merkel has made them since the 1800's
In order to determine the age of Lefever shotgun, the serial number must be known. However, Lefever shotguns were only made and distributed between 1885-1916.
The age of a shotgun can be determined by referencing the serial number with the manufacturer's records. In this case, the Winchester Model 12 shotgun with serial number 705000 was manufactured in the early 1940s. To determine the specific model, examine the markings on the shotgun such as the barrel roll markings or receiver stampings, which will indicate the model variation.