Bomb Release Control-Intervalometer, Type AN-B3 Vietnam War to obtain an accurate bomb

to obtain an accurate bomb run

which would have the ground map of the terrain below

indicating a manufacturing date of 1958

It is clearly 'experienced' but the dial markings are clear and the glass and case are intact

The binding is intact

Bomb Release Control-Intervalometer, Type AN-B3 Vietnam War to obtain an accurate bombThe Bomb Release Control (Intervalometer) permitted a bombardier to control the number of bombs dropped per release and their impact spacing. This would be used to set up a carpet bombing run, for example, over a large railroad marshalling yard, vs a more concentrated drop over a specific site such as a ball bearing factory. The left dial selected the spacing interval between bombs at a given airspeed, while the right dial selected the number of bombs