Found! Two dozen of these amazing pieces of sheet music. They range from Edwardian through to the 40s.
I have no idea what to do with them as I don't even play the piano - maybe I'll frame some or use them for craft projects - but I couldn't pass by such an historical treasure trove.
While a lot of the music sheets look Edwardian, this rather special book (above and below) appears to be Victorian. It isn't dated but has facsimilies of images 'in the possession of her majesty the queen'. Victoria was on the English throne from 1837 until 1901 but with a little detective work I've narrowed the book down to between 1857 and 1876, so it's at least 135 years old!
Yes I'm afraid you did read that right. I was going to add a close-up photo of the questionable lyrics of this song but on second thoughts maybe it's best to leave our investigation of this racist curiosity there.
This piece dates from 1902 at least, though the 50p price tag was added somewhat later.