MAKER: Sidle &. Co
MODEL: No. 2
c. 1881
SIGNED:J. W. Sidle & Co, Lancaster, PA, ACME
SERIAL NUMBER:350
AUTHOR: Barry Sobel, with the assistance of Brian Stevenson
Editor: Joseph Zeligs
The substage is focused (up or down) on the tailpiece by rack and pinion. A control on the right side controls forward-backward centering of the substage ring by rack and pinion.
The slightly larger knob on the left side of the microscope controls left-right centering. 
The substage The tailpiece can swing right or left:
The forward-backward centering mechanism of the substage ring that holds accessories such as a condenser or polarizer is illustrated here in the folowing four images:
The right-left adjustment of the substage centering is in an arc:
The substage support is L-shaped. The substage centering block sits on the base of the L
.
Right-left movement is in an arc around a pivot that is formed by the screw through the bottom of the L
. As seen here, there is a pin, fixed to the bottom of the substage support L
, which protrudes up through a cutout of the substage centering block(red arrows). The U-shaped spring registers against this pin and the inside of the cutout, pushing the focusing assembly to the right side of the picture, while the control knob screw pulls the assembly to the left side of the picture when tightened against the pin.
The following image shows the bottom side of the L-shaped support illustrating the screw that forms the pivoting point for right-left motion:
