Accutron

The date code on the caseback dates the watch

Bulova stamped a date code on the caseback: a letter for the decade with a digit for the year within it — L for the 1950s, M for the 1960s, N for the 1970s, so M7 is 1967 and N0 is 1970. It is beside the serial number. This is one of the better dating systems available on an American watch of the period and it is on the outside of the watch.

It hums and the seconds hand sweeps without steps

Hold the watch to your ear: a running Accutron produces a continuous high tone at 360 Hz, not a tick. Watch the seconds hand: it moves genuinely continuously, with no increments at all. Neither behaviour can be produced by a mechanical movement, which steps at its beat rate, or by a standard quartz, which steps once a second. This is as close to a conclusive single test as this catalog contains, because it follows from how the movement works rather than from how it looks.

A non-running Accutron is a service question, not a verdict

These movements need a specific battery voltage, the index and pawl fingers are delicate, and the coils fail. Servicing requires a watchmaker who works on tuning-fork calibers, and there are not many. A silent Accutron is extremely common and says nothing about whether the watch is genuine — get it powered before drawing conclusions, because the humming test is the strongest evidence available and it needs a working watch.