Dating a Wagner cast iron can be tricky but fortunately, Wagner is easier to date than its contemporaries because the evolution of the company and its logos through the years are well documented. These provide valuable clues that can help give you the approximate date your cast iron skillet was manufactured.
The first step is to take note of all the markings on the bottom of the pan and where they are placed. The Wagner Manufacturing Company used several logos and other designations (like “Sidney, O”) through the years. Some pans made in the earlier days of the foundry do not have a logo at all. Some also carry additional size designation that is usually a number, the most common of which is “8”.
Then, look very closely at the construction of the pan since it can also provide clues to date your cast iron pan. Very old Wagner pans have a raised ring around their bottoms to keep the pan from direct contact with the top of a wood stove that was used then. Take note also of other things such as the handles and how they are connected to the body.
Consult a reputable guidebook that many enthusiasts and collectors use. Compare everything you have gathered about your cast iron pan with the pictures in the guidebook. Special attention should be given to the markings on it and compare them to those listed in the guidebook.
You can also discussions on a forum for Wagner collectors and enthusiasts. They can help you date your cast iron pan. Or, you can ask a professional appraiser to help you determine the date when your cast iron pan was manufactured.