Audio Research cd8 production date

Is there a way to find the production date of a ARC cdp 8 based on the serial number other than the original invoice, which in this case is missing?
The situation in short, I have bought an ARC cd8 from a hifi shop in U.K. which claimed the item was 1 year old, after receiving it I had to open the case in order to install the tubes and I saw year 2008 on the print plate; looking better through the delivered papers I couldn't find any original invoice to backup the claimed age which increase even further my frustration (the provided remote control matches my ls26 but it doesn't work with the cd8).