I'm sure this discussion over the original introduction date of Nervex Professional lugs was covered some years ago on the list and the consensus back then was that they were first seen in the UK at least, in the late 1940s though the earliest Scot I've seen and owned with them fitted dates from 1952.
See
http://www.flying-scot.co.uk/
in comparison with the later set ;
http://www.flying-scot.co.uk/
Bob Reid Stonehaven Scotland
http://www.flying-scot.co.uk (mapped)