Instructions
Remove the photo from the frame and look at the back. Sometimes photographs will be hand-dated.
Examine the front of the tin, especially around the bottom, for an etched date. Oval tin frames used for special occasions were often etched with names or dates.
Examine the photo for chronological clues, such as period fashion or items in the background. For example, if a telephone appears, the photo is probably dated after 1920, although this is an approximation.
Take the oval tin to a professional antiques appraiser or jeweler. An expert may be able to date it within a narrow time frame.