The 1937 quarter is easily available in circulated grades. In Gem MS65 condition, it is somewhat underrated. The most common Gems of the the 1930s are the 1935, 1936, and 1939. It's really all about the mintage and the number of coins that were saved. The 1937 is usually considered the "next in line," but it is arguably more difficult to locate than the 1934 and almost as tough as the relatively low mintage 1938.
The typical 1937 mint state example is well-struck, white and frosty. This coin comes nice and Superb Gems are available if you look for them.