For adults I do first three letters of morph (or of each morph in a multiple trait) then two numbers for the year, and 2 numbers for the ID with males even and females odd. So PAS0409 is a female pastel born in 04 and it's ID number was 09. For babies (since I'll sell most) I started doing first three letters year cx (x being the clutch #) and one letter for sex with a unique ID. So SPI09C1F1. A little convoluted but it works for me!