I agree with you that an unmarked pharmacy/lab bottle isn't going to have much value. And my experience with VT meds is that those sorts of small and plain generic labels generally aren't all that valuable on their own.
Well, I ended up soaking it for ten minutes and spent another ten with a razor-blade in separating the two labels. Beneath was a label from a Wolfinger & Gilligan, Druggists, from Hopkins Station, Mi (500 people at the approximated time). Still a 'Spirit of Turpentine'.
But now I have a loose label and a really dark label. Is there any safe way I can lighten the original label or remove the old turpentine from it, so it can be easily read?
Wow I'm surprised that it's a label from a different store under there! I imagine that Roussin must have bought old stock from Wolfinger and Gilligan. Glad to see you got it off in one piece! I can't offer any recommendations about cleaning unfortunately.
Canadian Bottles, underneath the currently visible label is a different kind of paper. You can see its outline below (darker chunk centre right), but in person (with a panel of 9 ultra LEDs) one can tell it's a different kind of paper from the extant label.
From what I can tell and guess, Wolfinger & Gilligan bought this bottle from some supplier, ended up emptying it of its product (assuming it arrived full), soaked off the old label and threw their own over the remains. From there Roussin somehow came into it and nicely set his label over theirs.
As it doesn't appear anything is left to read on the even older label, I'm not going to remove the visible label.
Oh, and if it is of interest to anyone, the current label reads:
Spirit of Turpentine Dose - five to twenty drops on sugar. When employed as an liniment it should be used with care and followed by a soothing application. Wolfinger and Gilligan, Druggists. Hopkins, Michigan
Two different glues used back then. Sticky or dry. Peel a corner with a razor blade. If the adhesive is sticky it needs dry heat to remove. If dry it needs a wet bath to remove. Oxiclean and warm water by far works the best. Labels literally fall off. Dry heat is oven at 350 for about 5 minutes.