EIP model 548B 12 digit frequency counter; 10 Hz to 26.5 GHz (up to 110 GHz with optional sensors, not supplied) with a resolution up to 1 Hz, even at the highest frequencies. It has options 04 and 06.

Option 04 is one of the three Timebase Oscillators that were available as an option for this model.

and extended frequency (option 6) installed; the sensors and cables required for use above 26.5 GHz (band 4) are not provided. 

It also has GPIB (option 8), although some models considered it an option and some it was standard, as is the case on this unit. 

This unit was just NIST calibrated up to 26.5 Ghz. 

Provides leading digit blanking and user-selectable resolution. A keyboard is provided for commands and data entry. Uses a YIG preselector to select the strongest signal, within it's measuring range, on band 3 (1-26.5 GHz).This is a currently made product by Phase Matrix Inc. I believe the new price is about $11,000.

Very clean and undamaged. It is working properly in all respects. The two empty card slots are for options not installed. The crystal oven has it’s own power supply, and is on any time the counter is connected to the power line, to eliminate a warmup period. GPIB is installed; not tested, however. The cabinet is configured for shelf or table-top use; on the bottom cover there are four removable feet and a bail (tilt stand). The frequency display can easily be seen across a room, unlike some LCD counters.