Umm, doesn't the machine's badge tell you that? It should say one of the following:

1400cs/117

1400c/117

1400cs/133

1400c/133

1400cs/166

1400c/166

The 2nd number (after the "/") is the original processor speed. Alternatively, you can take the PowerBook's serial number to http://www.chipmunk.nl/klantenservice/applemodel.html and plug it in to learn your Mac's specs. Unfortunately, that page isn't loading for me right now...

Peace,

Drew