[SEL] Casting Filler

[Tod Engine]

What material was used for filling imperfections in castings around 1910 or so?  The Tod Engine castings have a filler that is dark grey in color and sort of looks like graphite when I hit it with a wire wheel.  Most of it is flaking off and eventually I will need to refill the castings when I go to do a professional paint job on her.

So what material was the original filler and what would be the material to use today?  Due to the size of these castings and inexpensive nature of bondo that's my first choice. 

Rick Rowlands
Executive Director
Tod Engine Heritage Park
William Tod 34" x 68" x 60" Cross Compound Steam Engine
Youngstown, OH
http://www.todengine.org/
Photo Albums Online: http://community.webshots.com/user/todengine!