The decoration on this tumbler closely resembles the Tiffin #203 etch, but it is covered with frit, which elevates the pattern above the surface of the glass. Documentation of Tiffin's use of this technique has not been found. Experts state that is not Tiffin.
Note that dark paper was inserted in the tumbler to highlight the decoration.
This water tumbler may be part of the Tiffin Corona line introduced in 1919. The #203 etch is shown on a Corona ice tea/lemonade/jug set on p.116 in Depression Era Stems & Tableware Tiffin by Goshe, Hemminger & Pina.