Milton Cross went inside the RCA Victor factory to see how records were made, in 1942. The process is almost identical to that used to make vinyl records, only with different materials. The original mould had a wax coating instead of nitrocellulose, but it was still electroplated to produce the master. (Though with gold and copper and nickel rather than silver and nickel). A “mother” was made from the “master” (which was then retired to the archive). Then, the mother was used to make a negative “stamping matrix” (coated also with chromium, eep), which was then pressed into biscuits of “the finest shellac available” (and 19 other ingredients, not specified) instead of PVC. Make sure to behold the mighty Banbury mixer!
The labels are pressed into the disc during stamping, not pasted on later.
Oh, and the original recording was made live – as the musicians played, their “poetic tones” were cut directly into the wax.