What do letters like "FH" mean on pigment ink labels?

[SuppliesMaster]

 Does anyone know what the letters that are under the color of the ink mean?  In this image it's FH, but I've also seen others. What does it mean?? 

[shadowsports]

Greetings,

Maybe it's a lot number.  If you'd like a definitive answer, I'd contact Canon support.  1-800-652-2666