Hello, and first off thank you all that reply in helping me figure this out. I am currently bidding a job where there is an old Challenger Main Distribution Board, and according to the plans summited to the city, they call out, that the bus is 600Amp with a 400Amp main breaker, but after calling the city of Riverside (county i live in) they have in their records that it is a 800Amp bus with a 400Amp Main Breaker, there isn't much on the panel left for Nameplates or Serial Numbers to verify. And finding Catalogs online for Challenger has been quite a challenge. If anyone can help me or direct me in the right direction to find out how I can get the correct info on whether or not it's a 400A, 600A or 800A bus that would help greatly. I have left a message with Eaton to see if they can help any. Thank you all for you time and knowledge. I will try to post a picture of the panel soon.