I believe the 5100 s is real because I have one in my garage right now. I'm looking to sell it to a collector in Houston Tx, but who knows what will happen. The "S" mark is off the the far right of the model number. The power for the 51SB runs off the 5100. I'm beginning to think I need to recover the original blue/green wood crate it was found in. It appears to be used, but the crate had never been opened before. I honestly don't understand how that works together.