1859 1 154/2 No uncertainty of freedom should occur between the guard-pin in the lever and the roller edge.
1881 F. J. Britten (ed. 4) 125 Roller edges for Lever and Chronometer Escapements.
2000 J. Heard et al. in R. Perryman & C. D. Ellis 98 The lens did not have the focal length to allow the roller edges to be focused.