If you have any CLR laying around a 3 min. soak in it will take care of any build up. Plus it helps to clean out the inside of the adjustable. I have used it before and it works great. I follow that up with a scrubbing with gun brush that you can pick up at any hardware store. I usually use the brass one. They come in a set of three brushes. When I am all done doing that I use some metal polish that I got in the automotive isle at Walmart. It will take away any tarnish you have like you see on your handles. I have turned some real turds into diamonds using this method.
Hey man....scrubbing bubbles.....and or at least whitening toothpaste with a tooth brush.... If they're this clean with just hand soap.....go ahead and try a little tooth paste with whiteners in it....does wonders....
A FatBoy and a FlairTip SS both for $6!!! Talk about a SUPER SCORE! Here are products I use to clean my razors. Old soft toothbrush Dawn dish detergent Scrubbling bubbles Bar Keepers Friend Mothers Mag Polish I have a jewelry cleaner I use on my adjustables which seems to work well, but IMO isn't a must have item.
It's amazing how nice crusty looking razors turn out to be once they've been cleaned. If you don't have scrubbing bubbles yet, you can always open up the butterfly doors and run them through the dishwasher. (If you have one...and the wife doesn't catch you doing it).
After revisiting a search for fat boys I couldn't find any under $100. Seems the guy should've paid you to take it off his hands.
Happened to me too. A friend scoured flea markets and Goodwills(that's what he loves to do) and came up with a blue star Lady Gillette for $5. Not nearly as stellar a find as yours. None the less it was a thrill in the beginning. Some friendly advice. You can take it for what it's worth. Don't get trapped into wanting to buy everything you see. On the other hand don't pass up a steal like you just found. You're a lucky man.