I concur, it looks exactly like the Datamarine knotmeter/log I had on an 80s Catalina 25. There is a shop (DMI Marine) that was in the business of selling both NOS parts for the old Datamarine kit and new hardware designed to fill the same physical mounts and kind of the same “80s tech” role but with newer innards, however it looks like the sole proprietor is winding the business down after some health issues.

They do still appear to have paddlewheel kits and dummy plugs available for now. I replaced the paddlewheel on mine with a DMI part several years ago and was very happy with the company and the quality of parts; it’s a shame that it looks like the knowledge base and expertise is retiring with the one person who kept it going.