I bought four (I think!) copies of this manual recently, all printed some years apart, giving me a good spread of dates, right up to the most recent one that I already had.
I have loved browsing them since getting them and just looking, the oldest and probably thinnest edition, has a date of 1912 at the back, but no published date at the front.
It really does open ones eyes to how much photography overall, materials and darkroom practice etc. have changed over the years. I'm currently comparing some of the chemical formulas, to see how, if at all, they have changed over the years.
They were well worth the purchase price, of just a few pounds each.
Terry S