One Frequency Engineering Laboratories 50A30200 frequency meter/wave meter in used condition.  This waveguide wavemeter is variable between 7.5 ad 8.5GHz and in my spot checking, the center of the absorption notch they produce is less than 700 kHz off of the printed scale (gradations are 10 MHz), and typically are under 200 kHz at room temperature on the bench.  This wavemeter interfaces with WR112 sized waveguides for use in H band.  Condition of the units available is similar to the picture, with a top bracket with bearing for additional mounting, some tape residue on the barrel which slows but does not prevent movement in places, and silver plated waveguides which show tarnish - I only did a cursory dust cleaning before testing.