Did they have commercial hand cleaner 100 yrs ago ? It would surely have gone discoloured and a yukky colour even if they did ?
Have you seen what colour paint goes after a couple of years in the shed. (Not pretty)
They were too keen as mentioned to delve into the contents.
If it were me ,I would have immediately tipped the contents out if I had any suspicion there would be something inside the content. I wouldn`t "fish" around with my fingers into some thing that could possibly harm my skin after "brewing" for a hundred yrs .
It was ALL a bit contrived and staged for my liking .
Almost certainly another lovely little yarn especially contrived for the gullible on Youtube .