From about mid 1983 to 1986 the T model number is rarely stamped on the frame leg because it is shown on the speaker label.
An extra single letter is apparently just an ‘inspection letter’ and can be ignored.
For dating purposes it is useful to know these are only usually present on speakers made between 1969 to 1976.
The date code is still on the front gasket but with a smaller font size.
Any greenback speakers with pre-April 1968 date codes printed on the chassis leg are likely to be fakes.
For 12″ speaker models, use the stamp location colour codes to guide you.
If you need more help, scroll further down the page for a more detailed explanation.However, I do not recommend using the stamp formats as the main basis for dating your speakers.The problem is, Celestion were not very consistent with them and this confuses a lot of people: I have included the stamp formats in the year column headers on the chart if you want to use them.All Celestion date codes contain a pair of letters representing the month and year the speaker was made.In most cases the first letter represents the month, and the second letter represents the year.Note – Ceramic guitar speakers (greenbacks) first appeared around 1964 / 1965, so it is highly unlikely you will find any earlier than this.