Hi Paul, the numbering system is split into Year Year /Month and then the
number produced that month. The YYM is usually the top but I suspect there
has been a mis=stamp here. Since Claud Butlers were bankrupt and in
recievership by 1957 it cant be 1965/February. So either the two are mixed
up top to bottom making the frame built in 1955/February and they had made
652 frames that month. That sounds like a lot to me esp,. as sales were
definitely tailing off by 1953. So I am going to suggest that the first set
of numbers are the wromg way round. So that makes it 1952/June. !950 - 1952
were the peak production years for British lightweights so that works. It is
really down to the lug work and brazeons on the frame to confirm this.
Certain features like roller cable guides on the bracket were in vogue for a
year or 2 then went out. If you can send some photos it would help. There
may also be a letter stamp under the bracket which is the builders code. I
know a few of those.
Mark Stevens Evanton Scotland