This 1 in. objective consists of two plano-convex lenses. The large lens (B; dia=13mm, f=33mm) is mounted on an inner sleeve. When assembled it is approximately 5mm from the front lens (A; dia=9mm, f=25mm).
The 1/12 in. objective consists of two plano-convex lenses. The inner lens (B; dia=7mm, f=8mm) is mounted on a spring-loaded sleeve, which is actuated by a numbered (0–9) sleeve (C) that acts against a brass collar (A). The front lens (dia=1mm, f<1mm) is mounted on D.