Circa 1900: Emulates glass made between 1900 and 1950. This is Restover Light from Schott. Made in Germany.
Restover Plus: Emulates glass made prior to 1900. More wavy than Circa 1900.
Polish 1, 2 and 3: Handmade glass that emulates glass made prior to 1800. Varies in thickness. Not recommended for windows larger than 2 square feet or in operable doors.