With all the interest in new brands of bitters (often inspired by historic recipes), Angostura bitters is always in my bar. It has a unique taste which I find essential for whiskey and gin compounds. Often I will have just whiskey or gin and bitters alone. Recently, I found a bottle of Angostura bitters from about 30 years ago, which I must have bought myself and left at my mom's house all those years ago. I compared it to the same brand as available today. The old one was slightly darker and seemed deeper in flavour and also more bitter, with a quinine-like sharpness the current one doesn't quite have (good as it is). I suppose after all that time in the bottle, the old one might have "aged" or concentrated further. Or perhaps small production differences will manifest after a generation or so, as we have seen with some (all?) whiskeys. Both were excellent. A bitters "vertical" tasting.