The Tektronix Type 184 is a compact crystal-controlled time mark generator. It is solid-state except for six 7587 Nuvistor vacuum tubes. The generator produces push-button selectable time marker intervals from 2 nanoseconds to 5 seconds.
There are also seven push-button selectable trigger pulse rates from 1 microsecond to 5 seconds.
The 184 contains a 10 MHz crystal in a 75°C oven. The frequency is specified to be within 0.001% of 10 MHz at ambient temperatures between 20°C and 30°C. In the same temperature range, the frequency is specified to vary less than 3 ppm (30 Hz).
The 184 was introduced in 1966 and discontinued after 1971.
Cartoon in schematic: Slow Sign (at delay line)