Nordost Serial Numbers

Nordost always sounds good on my setup but unfortunately, I would prefer to buy them used. Apart from being cheaper, they're more likely to be burned in and boy, I really hate running in cables. So, I would be grateful if more experienced users could give me more information on their serial numbers. I have heard that the serial numbers are attached/engraved, whatever on the cable itself for higher end series and only on the box (printed or labelled?) for lower end series? Are these observations correct? And are there serial numbers right from the very beginning or did they start at a later time? I have thought of asking Nordost themselves but not being a direct customer, I thought it's better I ask here. TIA!