This high Q cavity wavemeter for 10GHz is accurate to 1 MHz and dates to 1980. The cavity is attached to a length of waveguide 16 and is tuned by a drum micrometer from More and Wright. The larger circumference of the two inch drum micrometer offers a finer resolution. To maintain accuracy the lead-screw would need to be a very high quality component and thus expensive.
The micrometer head is fixed into the cavity with the screw that is seen near the top of the black cylindrical cavity in the picture.
The commercial wavemeter from Wayne Kerr uses the same type of drum micrometer and is terminated with a detector diode. This wavemeter was designed for in-line use within a piece of equipment. The design follows that published by the RSGB in the VHF Handbook.