NavList:

Frank, Gary LaPook is probably the NavList resident expert on the Polhemus computer, but I can take a stab at it.  I'm sure Gary will have corrections for where I go off the rails.

One of the things the Polhemus solves for quickly is the running fix with corrections for speed and track of the aircraft, Zn of the object, latitude of the AP, and Corilolis.  It provides the per-minute rate of rise/fall of the body and for the motion of the observer.  These are the MOB and MOO.  MOB and MOO tables can be found in the Air Almanac but using the Polhemus is faster and the sign of the MOB/MOO is easy to determine off the Polhemus.

The back side of the Polhemus has a plotting circle.  With it, the Nav can quickly draw the lines of position for the fix - and if we apply MOB and MOO, the LOPs are already "advanced" as if doing a running fix.  It is possible to also use the plotting circle to generate average winds aloft for the last segment and then to provide a track from the fix to the next waypoint - all quite quickly.

I frequently use my Polhemus - as I am not moving, I use Motion of the Observer as 0 - and I've gotten some very pretty fixes with it and a Kollsman periscopic sextant.  At one time, I wrote a primer on how to set up and use one - mostly for my own memory cribs.  I recall that I made a math error somewhere in the first example (with pictures) so never "shared" it.

I'm sure Gary LaPook can provide more details.

It is interesting you mention the B-58, Frank.  Bill Polhemus was a B-58 Nav.  William L. Polhemus | This Day in Aviation

The back of the E6B has a rotating wind grid - for fun, I've plotted celestial LOPs on it (again, I believe I was just following up on a comment by Gary).

As for a "good" price, I got an unissued one with manual and precomputation forms for $70.  A complete Polhemus computer will have the main whiz wheel and then 6 clear overlays for the plotting side for various latitudes.