(Calibrated by Fenns of Farnborough)
Later DC6 era pressurized planes could not use the perspex astrodome bubble fitted in the roof as in the DC4 / Catalina era planes, as the pressurization would not allow the bubble window. Instead they had a special window frame built into the roof near the rear of the flight deck through which a periscope sextant was used. Straight out of Ministry use , comes in black aluminum case with carrying handle.
measures: case 17.5” h x 12.5”; periscope 16.5” h, 15.4 lbs