Yes that's all black stuff from the 1970s gasket disintegrationWell, from your movement photos, both the case and the movement are pitted and the case back gasket appears to have disintegrated 😳
Well, from your movement photos, both the case and the movement are pitted and the case back gasket appears to have disintegrated 😳
And, as you’ve probably already discovered, the 31****** movement number makes the watch a 1960s watch, albeit 1969 so, with a disintegrated gasket that has ‘spilled’ into the movement, your 55 year old vintage watch is probably in need of a competent professional service.