value of 10 gallon red wing crock

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We have a 10 gallon Red Wing crock in mint condition,it has patent date of Dec 21,1915 on it.I believe by the size of the wing and the oval stamp that it was produced in the early 20's.We were told that the value was approx.25$ per gallon of the container.Could anyone help us determine if this value is correct. Thanks Tim and Tammy Dalhoe