>From the look of the lugs and the very slack 68/69 degree angles on the Maclean recently brought to the List's attention, this frame is without a doubt a 1930s one. The short scolloped out seat stay top is another feature of 30s frames although they were still found well into the 40s. Companies such as Claud Butler, Granby, Selbach, and Hetchins used them regularly, as I think that they came as part of a lugs, bracket, crown set, possibly made by Chater Lea or Brampton. From memory I think that the seat lug had a small spigot cast onto each side of the lug, onto which a hole on the inner face of the seat stay eye located..very neat thinking.
As for dating Maclean's frames, other List members have more or less covered what little actual knowledge that is out there. Presumbly the intial letters of the number changed each year, and equally presumably the second letter indicated the month of the year.
There is on record frame No EE212 which is known to have been a 1934 one; this fact has been documented by Murray Maclean the Maclean marque enthusiast for the V-CC. He also has ab record of Frame No DE517, but the year of manufacture is not known. FWIW..I think that the CR frame, No DB928, was probably made in 1933, possibly in February, with the number just being a sequential one starting at the beginning of the year, although that does sound like a lot of frames. The newly-discovered website http://www.classiclightweights.co.uk has an informative section on Maclean frames in the "Classic Framebuilders " section.
Norris Lockley...Settle UK