Recently one of these came into my possession. I suspect that it is a cannon quadrant from a naval ship, as it was splashed with the chipped remains of white and light blue paint. On the internet I cannot find anything quite like it.
On a wooden base, with brass plumb and brass readout up to 40 either side of 0, it was covered in black dust and badly splintered. Reluctantly I took the decision to clean it and repaint it, as it looked to have been painted several times before. The weighted plumb needle swings freely left - right.
There were quadrants used for measuring and mapping throughout Japan, and then there were gunners' quadrants which seem to be related but different.
The leader of our teppotai proudly displays a fine and very rare brass quadrant, but secretly I suspect that it is a land survey version, and not for artillery.
There was a good example on the internet dated from Tempo, with the measurements in oriental increments, but this one looks 'western' to me. Too early for 'modern' battleships, I get a feeling of Meiji from it. There is no lettering anywhere, solely these elevation measurement numbers.
Sizes, 25 cm across, 20 cm high, 2 cm thick. About the size of an individual cheese board. The needle actually swings out to about 45 degress, but is stopped by the upper cap sides.
Mon Cher Piers, Yes it is off a boat. A gunner's quadrant has to have a system to register it with the axis of the bore of the gun. You will note the one in Takeo has a flat base that could be aligned along the top of the barrel or possibly on a straight-edge placed in the bore. Many gunner's quadrants are shaped like a L with the long arm to fit the bore and the shorter arm forming the quadrant. Ah well Ian B