W5200 Ethernet Shield 2.2 MAC Address

I’m curious about the MAC address. There are some docs about this shield that say there should be a sticker on the back with it but mine doesn’t have one.

Is the MAC address hard coded or is that why in the programming code it sets the MAC address?

I know the MAC address is supposed to be unique on a network so if I have several of these Ethernet Shields on my network do I just make up MAC address for each of them?

I can get the MAC address of all my devices on my network so I can make sure I don’t have any duplicates.