Well I took the thing apart, was nice and simple.
Only thing I noticed is that the hammer, which was essentially a sand cast iron cylinder, had two bearing surfaces where it spun the the 'barrel' which were totally unpolished, and there was a bit of gunk in there.
Cleaned everything up, polished the bearing surfaces on the hammer, re-oiled it and it certainly sounds very lively, but don't have anything to test it on.