Losmandy GM-200 tangent arm mount. Worm bearings have been upgraded to reduce tracking error. The mount is blue and black, comes with Fiberbilt (I think) cases for each half, tall and short legs and two different piers for each set of legs for use with Newt or Refractor, built-in encoders, large JMI computer (Max?), Losmandy electronics and hand controller. Also includes Losmandy vibration dampers and height adjusters for one set of legs that are transferable to the other set. $4900 plus shipping. There are three or four threaded counterweights and a homemade spreader for added stability. Mount condition is excellent, threaded counterweight bar has screw marks from tightening weights, as is typical for this design after use.
This is a great imaging platform. Capacity specs are similar to HGM200 and used to be posted on Losmandy's site.