NavList:

Love your comment, Frank!

And I am also late to this discussion, but my small contribution is the pic (below) of a Quintant from the British Hydrographic Office, which I donated to the Rumsey Map Center a few years back. A neat detail is that the handle is hinged, making it easier to hold the instrument horizontally, but still able to fold easily so as to fit it into its leather case.

Here is the caption I scribbled for it in connection with a recent exhibit (I make no representation that it is accurate!):

Topographical Quintant (or “sounding Sextant”)

Cary, London, for the British Hydrographical Office

Late 19^th century

A quintant is a double-reflecting instrument so-called because its arc describes one-fifth of a circle, larger than that of an octant or sextant. Its primary function was measuring horizontal angles, for which a wider arc was useful. 

This quintant belonged to the British Hydrographic Office, and was used from shipboard to map shoreline features for hydrographic charts. 

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