I have. Just today I did this.....
I purchased this Acctim alarm clock last year, during my crazy eBay binge. Its fully-mechanical! Yes, you can buy a mechanical spring-powered clock made this century. That's why I bought it. Cost me less than £10.
Now, I do already have some form of alarm clock at home when I bought this. So why did I do it?
The answer is above.
Yes, I bought something just to take it apart.
In fact, I bought a few things just to take them apart. It's only now I got the time to do this teardown. And more are planned in the future, so watch out.