Lodge started putting SK (meaning skillet, DO meaning dutch oven, etc.) on their products in the mid '50's and added "made in the USA" in the mid '60's. The number and the SK are in the 12 O'clock position, which is typical of Lodge. I'd say, it's Lodge and was made in the decade prior to the addition of the "made in the USA" designation. (Mid to late '50's to mid '60's.)