The Mount Vernon line was introduced in 1931 and some items continued in production for more than 2 decades. This line was a modified version of the Stratford line that had larger diamonds in the pattern.
The Seashell line was introduced to the trade in early 1935. For a time in the late 1930s, select items made in crystal were sold as Kyrstolshell. Kyrstolshell versions have a smooth interior while Seashell items have shell details on the interior. The use of the name Krystolshell was discontinued by June 1941 when all items were sold as Seashell. Both versions were made from the same mold using different plungers with and without shell details.