Close Honda S 800, the 600 had round indicators and different grill . Owned one back in the 70’s, blew the engine on the A34 giving it some beans. As you say rare and fetching silly money now .
This one may test you @docjohn! I’m afraid it’s really difficult to take photos as you’re passing by on the boat.
Remember, back in the day, you could identify cars from their lights and hub caps. I'm sure a little lad when on tv to astound us with his knowledge.