Once proof coinage resumed in 1936, it continued until 1942, which was the first full year of active US military involvement in World War II. By that time, the US Mint switched gears and once again put the production of proof coinage on hiatus due to the need to focus on striking circulating coinage to nourish a hungry wartime economy.
The scarcest proof Walking Liberty half dollars are those made in the 1930s, though all Walking Liberty proof halves are considerably scarce. Enthusiasts with deep pockets prefer proof Walking Liberty half dollars with deep mirror surfaces and frosted, cameo devices. Such pieces are extremely desirable yet also very challenging to find and virtually always command a healthy premium over listed prices when they hit the market.