Simon Bird asks "Does anyone know when the name change occurred?..."
Alp brakes listed: 1956 Brown Brothers catalogue 1952, 1955, 1957 Holdsworth Aids to Happy Cycling catalogues (no Alp or CLB brakes listed in later catalogues)
CLB brakes listed: 1955, 1958 Ron Kitching Everything Cycling catalogues
As you see, there's overlap. Perhaps some retailers list their Alp stock on hand in their catalogue for some time the name changed to CLB. The appearance of CLB in the Ron Kitching 1955 Everything Cycling catalogue seems to be a better indicator for the name change.
Peter
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Peter Brueggeman
La Jolla California USA
4peebee(at)peterbrueggeman.com