How to determine the date of the first sale of a Patek Philippe

Patek Philippe certificates hide some secret codes, including the original sale date... decoding.

During the second half of the 20th century, Patek Philippe used to write a code at the bottom of its original certificates. Insignificant to the layperson, this code informed about the date when the watch left the factory and/or the retailer. This 4-letter code is actually quite simple to decipher, provided one has the right key!

Although the serial number of the caliber can inform us about the year of the watch, we will focus on the certificate

Illustration of the original certificate of a 3940	The "PONN" code present on the certificate

This is a simple letter = number correspondence, and reads as follows:

Letter	Number
P	0
A	1
T	2
E	3
K	4
H	5
R	6
O	7
N	8
S	9

The certificate above with the "PONN" code dates the sale to P=0, O=7, N=8, therefore 07/1988

Note that there can sometimes be a difference between the date manually marked on the certificate by Patek Philippe or the retailer and the date corresponding to the code: this is notably due to the uncertainty of whether it is the factory exit date, or the retailer's sale date.

Illustration of the original certificate of a 3960	The "PRNS" code present on the certificate indicating "06/89"