Originally Posted by gridplan

Thank you. I didn't know until now how to decipher that type of code. But what I was describing is different. On the metal plate of my 1966 Brooks saddle is A66. While I understand the 66 means it was made in 1966, the meaning of the "A" is no longer known. From vintage-trek.com,

"The stamp denoted the month and year of manufacture. Mrs. O'Donnell* writes: "Unfortunately, the 'code' book is now lost so we cannot decipher the actual codes used at that time. It is, sadly, not quite as simple as A=January, B=February etc.
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*The above Brooks information was provided in an e-mail from Mrs. E. O'Donnell in the Sales Department of Sturmey-Archer, when that company owned Brooks. Mrs. O'Donnell was writing to Robert Williams in response to his query about date codes. Our thanks to these two individuals and to Larry Osborn, who secured a copy of the original e-mail."

I ask because this has come up before on the Classic Rendezvous mailing list (and probably here, too). She seems pretty certain the letters do not straightforwardly correspond to months.