Does look a bit odd but there is one way it would be safe to proceed. Make sure you collect in person BEFORE handing over any cash - also the seller says they will provide proof its legit - ask for the serial number and check it with Raymarine.
Its a good price at the moment, but these things have a habit of going up at the last minute.
As Codprawn suggests, ask for the serial number and tell the seller you will check with Raymarine. Who probably won't be able to help by the way.
The Unit is in Winchester, and bearing in mind the amount of people Raymarine have made redundant in the Portsmouth area lately you might get a worried reaction
