Colchester Student, Master and Dominion Lathes Mk 1 and "Mk. 1½" (and other versions, by Clausing the 13 x 24 and 13 x 36 etc). Round-headstock model but with either a "sliding-lever" on the apron that lifts into either one of two slots to engage the power feeds - or with a single, centrally-mounted round control lever. The differences between Mk.