I'm always looking for ways to date old radios. For example, a Phillips-headed screw head would not be expected on pre-war sets.

When did split lock washers become common?

Hi Doug

Split lock washers were used in Atwater Kent Model 37 in 1927. Even Radiola III from 1924 used them. Probably available before radio?

Norm

:I'm always looking for ways to date old radios. For example, a Phillips-headed screw head would not be expected on pre-war sets.
:
:When did split lock washers become common?

What is pre-war? Is this pre-1940? My Silvertone 5761, which was made in 1940, has Phillips head screws on the motor board.

Thomas

Hmmm. According to this, Phillips-head screws began to be used in automotive industry in the 1930s: http://www.infoplease.com/askeds/10-20-01askeds.html