SUBSTAGE SLEEVE FOR ACCESSORIES
MAKER: JOSEPH ZENTMAYER
MODEL: 'GRAND AMERICAN'
c. 1865
SIGNED:J.Zentmayer, Maker, Philad' a
SERIAL NUMBER: 291
The substage assembly carries a sleeve(red arrow, left), adjusted up and down via rack and pinion. The sleeve has a removable cap (right) which has an RMS thread. The cap can be positioned on top of the sleeve to accept, e.g. an objective to serve as a condenser(as shown above), or on the bottom just to limit the bottom aperture.