05/13/2021

LP ("long playing") records
https://en.wikipedia.org/wiki/LP_record

LPs were introduced by Columbia records in 1948 and RCA Victor introduced the 45 rpm record, 7 inch with the big hole in the middle, in 1949. Both used the new "microgroove" technology, were made of vinyl and were considered "high fidelity".

By 1955 45s passed 78s in sales and 78s whimpered out existence after about 1957.

Stereophonic records didn't become wide spread until the 1960s. This was after the 78 rpm era. To the best of my knowledge there are no stereo 78s.