Reading Magnifier, 50mm, 12cm Focal Length Capacity_125mL Wooden-frame abacus with three U-shaped

Wooden-frame abacus with three U-shaped steel wires carrying 20 plastic beads each on a 13 by 6 inch base

25-inch base raises a magnetic needle to a 4

and bladder in anatomical position

this air-cooled rheostat carries a slide-bar carriage on a vitreous-enameled tube for variable resistance under thermal load

and 2 quadruple pulleys on a heavy composite base with capstan

Reading Magnifier, 50mm, 12cm Focal Length Capacity_125mL Wooden-frame abacus with three U-shapedChrome plated metal framed 50mm reading magnifier with a 12cm focal length, sized for fine print reading and convex lens image formation work in introductory optics.