I have a Brooks B66 that was bought new in the late spring 1978 in New Paltz, NY.
In the course of rehabbing it recently, I noticed it had a 3 character code 'O K 7' inscribed on the inside underside of the saddle top.
The first place I went to find out what the code might mean was vintage-trek.com. Alas, it appears that the Date Code key had been lost, according to a correspondent quoted there.
But I'm wondering...could the '7' be for the year 1977, then the 'K' for the month November?
Goodness knows what the first character--either an O or a zero, might mean...
Anyone have further anecdotal 411 to add?