Not all warrants are what they may at first seem and while a serial number may be traced it could easily lead to a product that was out of warranty before being sold.
Is the company still trading? If not , no warranty.
Is it a current model? If not do they carry spares? If not who is liable?
Is it warranted from date of manufacture or date of purchase? You won't know until you open the box and see if the certificate has been date stamped.
Is it a foreign model and laws applicable to the locale?
And so on and on and on.
Sales of goods act: The purchasers first and only point of contact is the seller your contract is with the seller not the manufacturer.
Bought it second hand, no contract with the seller, therefore no warranty.
Take it to any court in this land and tell them you bought it second hand cos it was a bargain, the original purchaser passed on the warranty without the seller's agreement and see how far you get.
We had a lovely old fashioned shop in Hitchin Neil might remember them, or knowing him be related to them, "Rumbelows Radio".
I went in to buy a valve for dad's wireless. "How many jew want boy I been waiting 16 years to sell one of them", could I expect my warranty to still be valid?
I'll give the ol boy full credit cos we went through his whole stock, all duff and then he not only gave me a full refund but also took the radio and attempted to give a free repair for the inconvenience.
You won't get service like that nowadays.
Any warranty is only as good as the person backing it, that person is only as good as the service they give you.