Grandfather clock designer or manufacturer. Each tall case clock maker has his own signature feature that marks his creation. You can find the company name printed or engraved on the dial faces or on its edge that may be clearly visible or almost unnoticeable and obscured..Do you have a clock you 'd like to know more about? You 're not alone. We receive several requests a week to identify clocks for people, and although we 'd like .If you own a longcase clock, determining its age can tell you how much it is worth. After 1880, most clocks were m.-produced by German and American .Identifying Grandfather Clock Styles. Determine the Age of a Grandfather Clock. Identify a Vintage Thomas Mantel Pendulum Clock. Oil a Clock. Check the Authenticity of a Howard Miller Clock..