Electrical item missing from under the seat. What is it?

Recently I acquired my uncle's 81 GPz550. It sat for probably 20 years until about 10 years ago my brother got his hands on it. Not sure what he or his friends did but everything on it that's been touched has something wrong or missing on it. I got my hands on it and I'm restoring it and trying to do it right. Rebuilt the front brakes, currently rebuilding the carbs, repairing the fuel tank and more. To the point: there's something electrical that's missing from under the seat. No idea what it could be. I'm waiting on a new battery so unable to test it. I've looked at the repair manual (I'm no electrician btw) and looked at diagrams on partzilla and am unable to determine what's missing. Anyone have an idea?