Kurt Sperry asks: "....how does one distinguish a Mk 7 from a Mk 6 and a later Mk 7 from an earlier one?
According to Gordon Selby's British Cyclo derailleurs article in The
Boneshaker 166, Autumn 2004, the badge on the Mark 7 derailleur body
appeared in four versions, two of which appear on the Classic Lightweights
page I referenced [ http://www.classiclightweights.co.uk/
There wasn't a Mark 6 rear derailleur.
Over their timespan, there were unnamed models of two-pulley Cyclo Benelux derailleurs [1950, 1952, and 1953], and named models of two-pulley Cyclo Benelux derailleurs [Sport, Tourist, Mark 7, Mark 8 Tourist, Mark 12, Super 60, and Sport P2]. There were variants as well, one example being the four different badge versions of the Mark 7.
Peter
Peter Brueggeman
La Jolla California USA
4peebee(at)peterbrueggeman.com