The 7 lb clamp on counterweight fits the 4" OD telescope brass tube with precision. Given it's construction, I suspect this accessory was probably made around the same time as the telescope.
I wonder if it's a Cooke item. The telescopes original owner, Dr. Hugh Walsham of London, had an interest in solar physics. Was this weight used to counterbalance a spectroscope?
This Cooke refractor is my first foray into antique instruments so I had never seen such a clamping tube counterweight. Neither it seems have the members of the Antique Telescope Society. One ATS member did mention that Unitron used this kind of counterweight. If anyone reading this has seen this type of counterweight on other instruments please chime in.
As illustrated in previous posts, I used it to balance the OTA on modern mounts when doing visual observing and imaging.
The "bottom" side of the weight has a flat spot that I assume is for clearance issues. When the telescope arrived I never did try the counterweight out prior to disassembly. When I have the scope together again for fit testing prior to painting I plan to try the counterweight out to see how it works with the OTA and it's other parts.
I'd like to paint the weight the same color as the mount, but I'm having a devil of a time popping the pin out of the pivot. Both sides are roughly the same diameter so it does not appear to be tapered. As it was the pin face was nearly perfectly flush with the side of the counterweight, as if the surface was ground after assembly. An ATS member suggested the pin ends may have been flared to prevent the halves of the counterweight from coming apart and I may have to drill it out. But I'm inclined to not do anything destructive. It may wind up on the shelf unpainted as I don't expect to mount a spectroscope on the focuser.