How to find build date for Magic Keyboard and Magic Mouse

I'm selling my 2017 iMac to buy a new Macbook Pro with large monitor for desktop use when I'm not in mobile mode. I have two Magic Keyboards and two Magic Mice from previous Mac computers but have not been able to find their build dates so I can sell the right pair of accessories with the iMac. I know one set was made in 2017...the other set could be much older. Finding build dates by serial numbers is a very tough exercise online and four Apple tech or sales agents could not provide phone call assistance answers. Is there a database resource that could identify when the two sets of gear were made?