Registering an "ancient" Deathadder - serial number unknown

I have a Deathadder I bought in April/May of 2007. I've been using it as my daily gaming/general use mouse ever since, and on the whole it's been unquestionably reliable. Just for kicks I wanted to see if the date of purchase or at least manufacture would show up in Synapse if I tried registering it, but the site throws the error message "Item serial number is unknown".



The receipt has been lost to time and several house moves later, and the chain of stores I bought it from went bankrupt years ago. It's not that big of a problem, to be fair: Obviously the warranty has expired already, and the mouse itself functions as well as any 13 year old mouse can do, but I was just curious I guess. For the record, I have no reason to believe that it isn't a real Razer product: The chain I bought it from was a well known and reputable dealer of electronics, and Razer wasn't a very well known (i.e. a target for scams)



Any suggestions or help?