ISI Testing results highlighted a discrepancy for this level. Scott and I did a peg test and saw the horizontal crosshair was not normal to the vertical rotational axis by 40µrad.  This isn't much for a survey instrument but amounts to .003" over the 6' length of a HAM ISI Optical Table.

Hugo & I adjusted this to something less than 4µrad so we were pleased.  Even going from 40 to 4 was one of those measurement: put some pressure on the screw and when you think it might have moved, check because you might have moved too much.

We had this instrument for something approaching a year now and it has been around.  We have two others and they should certainly too be checked.  This one may have crept out of adjustment or it may be that the factory specs is only 100microrads.