Hi tmackinnon,
Is your iPhone connected to an accessory through a companion app, such as a health accessory, vehicle, or smart watch? This could be the reason you see the unknown accessory. If that's the case, disconnect the accessory and restart your iPhone. If you're unsure how to disconnect from it, reach out to the manufacturer for instructions.
If you're not connected to an accessory through an app, or if those steps don't remove it from your Bluetooth settings, reach out to Apple Support directly. They can be contacted here: Get Support, or by calling the most applicable phone number from this list: Contact Apple for support and service.
Best regards.