(disclaimer: these pages are not for commercially purposes; we are truly, genuine fragrance lovers examining hundreds of perfumes to understand the "meaning" of batch numbers, and here are the results)
Here we are going to investigate the -historically- most famous perfume house: Guerlain.
It's a bit difficult task, because Guerlain adopted several "letters and numbers", different boxes, and complicate batch-codes, indicating "Years" and "Months". So, we should have a look at: boxes, labels, symbols and perfume "launch date", simultaneously, to obtain an additional help.