How do you tell who made an Excel shotgun?

Answer 1

Only by comparing it to known products of the possible makers. Joe Vorisek's book lists the makers as Crescent, Crescent-Davis, J. Stevens, and Iver Johnson. But since Stevens/Savage bought Crescent and Davis, and operated them as a separate company for a few years then took over the line as Stevens, there will be identical guns from those three company names and no way to determine if it was made in 1925 by Crescent, 1930 by Crescent-Davis, or 1935 by Stevens.