78 RPM

The history:

Earliest speeds of rotation varied widely, but by 1910 most records were recorded at about 78 to 80 rpm[Edision's diamond disc etc]

In 1925, 78.26 rpm was chosen as a standard for motorized phonographs, because it was suitable for most existing records, and was easily achieved using a standard 3600-rpm motor and 46-tooth gear (78.26 = 3600/46)

Thus these records became known as 78s (or "seventy-eights"). This term did not come into use until after World War II when a need developed to distinguish the 78 from other newer disc record formats.

Earlier they were just called records, or when there was a need to distinguish them from cylinders, disc records.

The durations of 78 RPM recordings is about three to five minutes per side, depending on the disc size. If it is a 12 inch disc, it usually holds four to five minutes of music. A ten inch typically holds three minutes. 

The 78 format faded from the scene by 1955, when vinyl took over.