I saw a tweet from Sophie Haskins who is exploring her own A500 and discovered that it had an upgraded Agnus chip. The original A500 shipped with a set of chips which are referred to as the Original Chip Set (OCS). The second generation of the chips were labelled Enhanced Chip Set (ECS). A500s towards the end of their production lifetime were manufactured with some ECS chips instead. I had no idea which chipset was in my A500, but Sophie's tweet gave me a useful tip, she was using some software called sysinfo to enumerate what was going on. I found an ADF disk image that included Sysinfo ("LSD tools") and gave it a try. To my surprise, my Amiga has an ECS "AGNUS" chip too!
I originally discovered Sophie due to her Pizzabox Computer project: An effort to acquire, renovate and activate a pantheon of vintage "pizzabox" form-factor workstation computers. I once had one of these, the Sun SPARCStation 10, but it's long since gone. I'm mildly fascinated to learn more about some of these other machines. After proofreading Fabien Senglard's DOOM book, I was interested to know more about NeXTstations, and Sophie is resurrecting a NeXTstation mono, but there are plenty of other interesting esoteric things on that site, such as Apple A/UX UNIX on a Quadra 610 (the first I'd heard of both Apple's non-macOS UNIX, and their pizzabox form-factor machines).