Impressive Seatpost...
 

...and also an evolutionary dead-end. Obviously an attempt at suspension, but what tha…?

https://cimg5.ibsrv.net/gimg/bikefor...64f015645b.jpg

Cane Creek Thudbuster --

You must be pretty tall - some modern riser bars would do that bike a world of good

those posts are still made - they have evolved some since then though

https://www.backcountry.com/cane-cre...201bf00b192a84

Cane Creek Thudbuster. I used one for a few years and was favorably impressed, but it didn't work as well as "real" rear suspension. Well engineered, well made, but as the OP said, an evolutionary dead end.

Not my bike. Saw it on Craigslist and said my god, what is that thing? in the precise tone used by Wesley in his "to the pain" speech. Thanks for putting a name to it! :D

Currently available and selling like hotcakes for gravel bikes.

there is a seatpost in this picture somewhere.
https://cimg2.ibsrv.net/gimg/bikefor...9cc4c08477.jpg

This wheel keeps getting reinvented. I understand saddles with springs work pretty well and cost less.

Lots of people love it. When I was a mechanic we put it on customers' bikes all the time. Good for bikes where the customer doesn't care about the weight of the bike. They do work, not just "an attempt" at suspension. They're sorta heavy though. Cane Creek is now making a very expensive lightweight version of it.