Movable limit markers for viewing glass of measuring instruments

Apparatus for marking limits of a measurement in which a movable display means displays a measured value,

• said apparatus comprising a viewing glass having a front surface and through which said display means is observed,
• said viewing glass comprising an open arcuate groove extending parallel to the movement of said display means, at least a first displaceable marker located in said open groove being accessible to be manually displaced in said open groove to denote said marking limits, said groove in cross-section having a first portion which narrows inwardly towards the front surface to retain said first marker and a second portion which widens outwardly from the first portion to the front surface, said at least first displaceable marker comprising a cylindrical member freely slideable along said open groove, said open groove being of such size to permit said displaceable marker to be moved by finger pressure directly applied to the displaceable marker with the displaceable marker being slid in the groove by an operator to denote the measurement limit.