Double Concave Glass Lens, 50mm Diameter, 250mm Focal Length, 4mm Thick Subcategory_Inorganic Compounds with retractable hooks for tandem

with retractable hooks for tandem stacking during physics force experiments

Class-visible 12-inch demonstration meter with magnetically damped moving coil and Perspex front-and-back panels

Sliding-window gold-leaf electroscope with anodized aluminum walls and an internal scale

5cm brass rotor balanced on three pairs of adjustable cast-iron pivots

Double Concave Glass Lens, 50mm Diameter, 250mm Focal Length, 4mm Thick Subcategory_Inorganic Compounds with retractable hooks for tandemDouble concave glass lens at 50mm diameter and 250mm focal length on a 4mm thick blank, the diverging curvature softening divergence for subtler virtual image reduction in optics work.