You will have to call Mossberg
Depending on condition and age; 75-175 USD.
Go to proofhouse.com.
By the serial number.
The western field model 172B was made for Montgomery Wards(Western Field) by the firm Mossberg and sons.The Mossberg model 395K and your shotgun are one and the same.The Mossberg model 395K was made from 1963-1983.
This shotgun is a mossberg model 85. made between 1934-1937. dont know value.
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.
By the serial number
Your Western field shotgun is a Mossberg model 385K shotgun that was made for the Montgomery Wards company by Mossberg and sons.The model 385K shotgun was produced from 1960-1986,These bolt action shotguns are valued at between 75-110 dollars,for a gun with between 60%-90% of its original finish remaining and a good bore.