People (including me) sometimes use static IP and reserved IP interchangeably but they really aren't. Sounds like you are trying to assign these IPs a DHCP reservation? Usually these are assigned by MAC address in your DHCP server but the steps you need to go through vary in the specifics by manufacturer and model of whatever appliance hosts your DHCP server. If you're trying to assign static IP addresses using the IP stack of the end device (not really recommended) the way you do it depends on the device itself.
Many devices will have onboard Ethernet or WiFi chips made by someone else, and that’s what shows up when searching by OUI (the Organizationally Unique Identifier that makes up part of a device’s MAC address).
So whatever it is it's not registering with DNS. So at this point download a free prog called advanced port scanner. It will scan your network. It may or may not come back with a manufacturer name. If it doesn't look up the mac address to track down the vendor.