Bill, I don't know about the 680B but on the 8800s the first ones came with round handle switches. They (MITS) switched over to the flat handled switches with the 8800As but I had a late 8800 (the last one produced AFIK) and it also had the flat handled switches. I don't know if any other 8800s have been found with the flat handled switches or not. But I STRONGLY suspect that MITS was using nothing but flat handled switches even BEFORE the 680 went into production. Steve Gabaly was tracking the Altair SNs and features and he would be the one that could definitively answer your question. Also rattle Mike Haas's cage, he has three 680s and should be able to help. I've been told that MITs switched to the flat handled switches because the round ones got PAINFUL when toggling in long programs. Joe At 08:48 AM 7/12/05 -0500, you wrote: here goes again... I'm trying to build a replica of a 680B using a real 680B case from eBay, authentic switches and LEDs, and a power supply and CPU board of my own design. I've seen both flat- and round-handled toggles in pictures on the web and my old issues of Byte magazine, and have been unable to discern a pattern to it. Can anyone on the list tell me why the difference, and which one is more accurate to use? Thanks.