Ludwig I'm sure I have a photo of the two brass frames & that's all they were,and will search some more. I spotted the first on ebay & wasn't certain what it was, just to be clear. The seller included minimal information, yet I sensed it to be either a navigational or survey instrument perhaps associated for field artillery. The vertcal sight vanes were of course missing but I could make out what appeared to be & was a 360 degree etching around the circumference and looked to have been set up for a tri-pod mount.
The price was not extremely high & I won the bid & was really overjoyed when it arrived and inclulded an identical second base/frame. Without the second I would probably have just polished the first and used it as a paperweight. I started asking questions of experts in the fields mentioned beforehand and all recognized the Gurley name, which when Googled yielded large amounts of information about their other instruments, but initially didn't lead me to the keyword "sun compass". It was an old surveyor with a love of history who mentioned the possibility that what I had purchased was a Sun compass, but he'd only read about them and never seen one and neither would I for a few more weeks and much more study. During the process I realized that Gurley used most of the same parts & construction technology on various types of instrments over the course of several decades and the light came on & there was indeed joy to accompany the shock of discovering such a rare bird. If I could find a collection of 19th. century Gurly instruments I could inspect, photograph, measure/gauge & duplicate each thumb screw, pivot, elevator, sight vane, gimble, level, scale & compass. Even to the point of adding a brass telescopic sight (original not rebuilt) as a later innovation to the sight vanes. My photos (resized )fail to show the lovely and artistic detail of this hand built instrument...not my design but the faithful reproduction of a 19th. century artist in metal!I found such a collection in my own hometown! A semi-retired surveyor with an incredible collection of antique survey insruments that he loaned me access to for the 6 months I spent rebuilding my Sun compass that actually has been certified as functional to 19th. century standards. I'm not a surveyor and extremely limited knowledge of how this amazing gadget works, but it made me proud to hear the certifier pronounced it good to go & once again capable of charting a nation!
Ludwig if you know where I can purchase of an early days British navigational chronograph, please save me from myself and keep it a secret! Rick C.