The dollar bill was for tighter fitting areas like between the boiler and engine base of the 35 or under the steam domes.
Well I got that memory wrong Nick, I used to really like Rog's site and all the helpful hints he had (which was many!).
I believe Rog got the dollar bill gasket tip from me. It is .004" thick and very strong. They are perfect for replacing gaskets on a #20 or 4 screw cylinder #10/25 cylinder. Great for all other flanges and any place a thin sturdy gasket is needed.