Dating bardou telescopes
The rack is inset into the bar and held in place by two screws.
The stage with two stage clips has an opening made with a counter-sink and a disk that holds the aperture wheel fits into this there are notches on the disk and counter-sink to line it all up.
The main column of the microscope is topped with a compass joint that allows the instrument to be inclined when used in vertical mode.
Above this joint is the limb that carries the prism holder and the tube.
The stage measures 9 x 6.5 cm with a 40 mm center hole.
Focusing is by rack and pinion movement of the stage using a single milled brass pinion knob.
The bar that holds the mirror and stage is screwed into this limb with a blued steel screw.
At the rear of the limb is a milled knob engaging a brass washer loosening this knob allows the limb to be freely rotated where it can then be tightened leaving the tube and stage at any desired angle.
This instrument is signed in script on the tube Made for Widdifield & Cie, Boston.
The incomplete translation of the signature is indicative of its French origin. The microscope is very similar to the Chevalier Universal Microscope, but some details of construction suggest that it was made by a different firm.
With the examples made by Chevalier, the aperture wheel is mounted on a separate arm located under the stage.
The stage can be easily detached from the main body and reinserted upside down for use when the microscope is in its inverted configuration.