In the world of 68K Mac homebrew, the ROM Boot Disk concept has gained popularity. Surprisingly, only one Mac officially had the ability to boot the Mac OS entirely from ROM. This was the Macintosh Classic. However, for other Macs that can take a ROM SIMM, a ROM volume can be embedded in the Mac ROM, and it can even be mirrored to a RAM disk. Apple itself implemented a flashable Mac OS ROM volume in 1994 but only used it publicly in the Apple Interactive Television Box (AITB). The AITB was Apple’s attempt to enter the set-top box market, and it was used in trial deployments with cable TV companies. However, the product didn’t take off, and Apple never launched it for retail sale.
http://oldvcr.blogspot.com/2023/07/apples-interactive-television-box.html