The iPhone is not going to be covered by any kind of warranty......if that is what you are asking here.
For what its worth, your serial number does not start with "M", although it is possible that the Model Number begins with an "M".
All this tells you is that the iPhone was new when it was originally sold in Europe whenever that might be.
The purchase date of April 1978 would not appear unless someone has been into the phone and changed some things around.
At least you know that the phone is not much more than a couple of years old.
Are you able to get a Battery Health reading on the phone?