Hello, IBM changed the AT at least once through it's production run. The one I have is a later model, since it is an 8mhz system. Yours may differ somewhat, but I'll tell you what I can see. I find that same number (#8286121) on my battery. It's actually a Panansonic replacement battery BR-E3 6v and looks like a small black box with a cord and plug. It plugs in to the motherboard right behind the keyboard connector. Mine was held is held in place to the side of the case with velcro. I'm not sure if the velcro is factory or not. If your machine has been sitting, unused for sometime, I suspect that maybe someone took the battery for another use. Chad Fernandez Michigan, USA Elaine Benner wrote: