Serial or Lot Number on Back of Pins

I can't seem to find when the start date was when Disney began serializing or stamping the lot number on the back of pins. Does anyone know? I wouldn't say they are serial numbers as some pins share the same number, but rather it must be a lot number of sorts.

The reason I ask is because I have a Splash Mountain pin dated 2008 with a lot number stamp on the back. I wouldn't think the lot number stamping had started back in 2008, but this pin looks and feels like it's authentic.

I've seen some newer pins, like hidden mickeys and such, that do not have the number stamp even as new as 2013/2014, so I don't think every pin gets the serial/lot number.

Can anyone shed some light on this?

Thanks!

Going way back... Some (not all) of the limited editions would have serial numbers. Some would just have Limited Edition 500. Others were 001 of 500.

I don't know the rhyme or reason...

Side Story, there was a 2000 Fab 3 Fife and Drum pin released at Epcot on the 4th of July, LE 5000. I was over by Millennium Village and looked on the pin cart. Turned one over and saw 0005 of 5000. Wow, that's a low number. Pulled the next one, 0004. Really? Next one, 0002. Hey! What happened to 3? Oh well, yep, next one in was 0001. All mine, grabbed them all.

Still hasn't gotten me anything, but was cool at the time... Edition size is too big, but since they are low numbers, maybe someday...

Yeah, exactly. Good finds!