Old brown breadbox type with black-ish keys C64: always 6581

White "modern" style  C64C: depends, you have to look underneath, there's a ventilation grill at the front of the machine, if you see the motherboard through it, it's an old type motherboard, which means it has a 6581. If you don' see the motherboard, it has an 8580. The newer motherboard has  smaller footprint and this is why you can't see it through the grill.

Old brown style but with cream keys C64G (you probably won't find this in Canada): has 8580

Whoa, Thanks!

The general rule is breadbox = 6581, C64c = 8580, although this is not always true, because there was probably a transition period where Commodore put one type of mo-bo in the other type of case. And sometimes some people probably swapped the mo-bos for some reason. I was going to say that you could look in through the cassette port and determine where the SID chip is located. (Different SID chip = different location.) But then I found this:
http://ilesj.wordpress.com/2010/07/01/h … sid-model/
There are some really easy tell-tale sign for each mo-bo.

oh ok ! check for an old model then ! (good old breadbox)

Non je cherche une 6581 parce que j'ai déjà une 8580!!!

Was it an old breadbox or a C64C ?
Because if this is a C64C, there is chances that it got a 8580 in it ! (I'm sure there is another way to know it !)
Au pire du pireeee, j'ai un C64C avec une 8580 qui traine dans ma chambre si jamais tu veux dealer sa dude !

There is a C64 in the "pawn/antique shop" near my appartment. I noted the serial number: No. SC 232 346.
So, is it possible to know which kind of SID (6581/8582) is inside the computer by looking at the serial number? (Or by looking at the computer itself?

Thank you C64 headz,

Simon