Agilent HP 5345A DC to 500 MHz frequency counter with option 012 digital interface. 11 digit resolution. Frequency extension plug-ins available sold separately.
Agilent Keysight 53210A / 115 / 010 / 300 Frequency Counter. 10 digits/s. Includes 15 GHz channel and ultra high stability timebase options plus battery and GPIB.
EIP 548A - Microwave Frequency Counter. 10 Hz to 26.5 GHZ. Includes option 05 (best available timebase), and option 06 (frequency extension capability).