Monoyer's scale of visual acuity

Ancient scale of visual acuity, originally invented by ferdinand monoyer. White metal structure, black lettering on white plexiglass plate. Small curiosity on the french scales: by taking the first letter of each line from the bottom, we get the name of the inventor (monoyer) on the left, and on the right by taking the last letter of each line, we get his first name (ferdinand). Very nice decorative effect. It works with 21 X 254 linolite tubes, either in 20w or 40w depending on the desired degree of brightness. Dimensions: height 81 cm, width 27 cm, depth 12.5 cm.