Here’s an idea from 75 years ago that apparently never caught on. It’s a QSL “card” in the form of a recording disc. Using a recorder such as the Wilcox-Gay Recordio, the operator would record the other station’s signal. Then, the traditional QSL data would be written in with a “special marking ink.” The blanks were from the National Recording Supply Co. of Hollywood, California. The manufacturer promised “unlimited playback with wide frequency response and a minimum of surface noise.” The blanks retailed for a dime each. This example was shown in the May 1941 issue of Radio News.
The disc is marked “Copyright Pend. National QSL Disc.” The magazine’s April 1941 issue provided more detail. It noted that “recent developments indicate that many amateurs now possess recording equipment and, instead of the old-time postcard, now use a disc to record other amateurs’ talks and send them through the mails.”