This is my contribution to the "age game"!
The maker is Henry Shuttleworth (either junior or senior) of 23 Ludgate Street, London.
They made the whole range of "Scientific Instruments" between about 1765 and "juniors" death around 1810.
It is a standard front achromat from one of their telescopes with focal length of 9", F7..The cement (or oil perhaps) needs changing. The glass is very pale green. When I am brave enough to remove from the mount and reglue, I will be using it regularly!