Happy birthday to your Z80! It is a few months older than me - manufactured week 52 of 1976 :-)
Despite me being younger, Z80 influenced my life quite a bit, about as much as 8080 and 8086, and has a special place in my heart as an elegant, easy to use CPU. One of the first computers I worked on was a beautiful MSX2, based on Z80, together with Olivetti M24 (8086 based) and soviet 8080 clone based Radio-86RK.
I also regret that I didn't save my first computer or processor I ever purchased. To my excuse, I moved through a few countries, and an antiquated hardware wasn't on the top list of priorities to go in my luggage...
It wasn't until 2009 when I actually purchased a Z80 (CMOS Z84C0006PEC to be exact). Since then I purchased a hundred or more of them to be distributed with my projects/kits :-)