It is a light aqua octagonal bottle, 6 cm tall, with a burst top and full of swirls that are clouding the glass. "Blackwood & Co London" is partly embossed on it - since the bottle was too small "D" is missing from Blackwood and the last "O" is cut in half.
I've cleaned the bottle with Steradent Active Plus - fizzy tablets used to clean dentures. I let the solution work for 20 minutes and ended up with a slightly cleaner bottle, though not as sparkling as I'd expected. Actually I don't see much difference, do you?
And the obligatory Before and After