The interesting part of an older boat is older parts.
That's my knotmeter paddlewheel. Normally, this is the kind of thing that hangs just below the hull, not readily visible.
It's out of the boat because some of the little paddles are bent.
The company that made this has a long and interesting history on their web site. See http://www.dmimarine.com/faq/Q1%20sub.htm for a cool story about business and integrity.
I'm not dealing with a new, large company like Raymarine with a lot of corporate overhead. I can't pick this part out of a Defender or West Marine Catalog.
I'm dealing with a small, older company. They don't have on-line ordering. You send them a letter, fax or email or make a phone call. But the unit seems really well made, so there's no reason to do anything more than replace the broken part.