The most authentic experience is not an ISO at all, but a ROM dump. A "ROM" is the flashable firmware for a phone. Using tools like fastboot or custom recovery, you can flash an Android 1.0 ROM onto a real G1. For emulation, you can use an emulator like with a G1 kernel and the extracted system.img .
. Authentic Android 1.0 ISOs are extremely rare and often custom-built by enthusiasts from the original Android Open Source Project (AOSP) 2. Setup & Installation Guide Android 1.0 Iso
Curiosity: Seeing how far the OS has come from its humble, physical-keyboard-reliant beginnings. The Challenge of Finding an ISO The most authentic experience is not an ISO