T & H Doublet were recorded as working as opticians and instrument makers at City Road, Finsbury from 1853 to 1868 then moving to Moorgate Street. This level would be circa 1860's.
This instrument is complete with the original fitted leather case
I have done extensive research for Doublet on the internet and have not found much at all. I would love to find out more about this instrument maker if anybody has additional information.