Check out the motion on this Mogul, taken New Years Day:

http://www.railpictures.net/viewphoto.php?id=182395

Ah, the wonderfully quirky 640 class machines with outside valve gear and inside rods! The first good picture I saw of one was in a Pizza Hut restaurant; it showed the engine’s crew standing in front of the drive wheels, if I recall correctly. All of the chain’s restaurants were remodeled a few years ago, and the original black & white photos that used to be found in Pizza Huts disappeared.

-James Hefner
Hebrews 10:20a

Surviving World Steam Project

Quite a few of these are preserved, and operating. I have a color paperback text on these engines (in Italian). These came in a variety of valve gear and boiler configurations. Some had caprotti, some had funky feedwater heaters where the smoke exhausted above the cab.