a.lber.to
2357
Ahhh...
I did not realise you were referring to a Type XX watch - I should have read your post more carefully. As far as I know, all the watches in the Type XX/XXI families follow a different, independent numbering schema, and these make up the bulk of Breguet's sales. I do not know exactly how many of these have been made, but 40 to 50 thousand would sound about right to me.
As per the rest of the production, there are roughly 5000 numbers used for each letter of the alphabet, and the first series did not have a letter. Now, though I do not know precisely what letter is being used now, the "Tradition" I took pictures of in Basel this year was number 3175 T. Therefore, presuming that they have finished producing the T series and that they did not skip any letters in the alphabet, we could deduce that Breguet have produced roughly 105,000 watches thus far (5000 + 5000*20), excluding the Type XX/XXI.