Vinyl's lower surface noise level than shellac was not forgotten, nor was its durability. In the late 1930s, radio commercials and pre-recorded radio programs being sent to disc jockeys started being stamped in <answer>vinyl</answer>, so they would not break in the mail. In the mid-1940s, special DJ copies of records started being made of <answer>vinyl</answer> also, for the same reason. These were all 78 rpm. During and after World War II, when shellac supplies were extremely limited, some 78 rpm records were pressed in <answer>vinyl</answer> instead of shellac, particularly the six-minute 12-inch (30 cm) 78 rpm records produced by V-Disc for distribution to United States troops in World War II. In the 1940s, radio transcriptions, which were usually on 16-inch records, but sometimes 12-inch, were always made of <answer>vinyl</answer>, but cut at 33 1⁄3 rpm. Shorter transcriptions were often cut at 78 rpm.
What material were most mailed records made of?
vinyl