Just picked up a 1930s Battery operated Coronado

[old_tv_nut]

Note that later and more expensive scopes may have built in measurement cursors to get a more precise measurement of time/frequency than just eye-balling the display, but eventually these have to be calibrated against a standard frequency source.

Really modern scopes are all digital sampling types, and the sampling rate is crystal controlled, so the scope really contains a calibrated reference.