I've used the search function and of course seen the two stickies at the top of the forum. I've gathered so far that the numbers on the bottom of the bottles indicate the year they were made, and that the older stuff is greenish, and at some point in the past they switched to brown/gold. Is there a comprehensive list of which codes correspond to which properties? How many times has the actual formulation changed? Last night I bought some bottles, and there was one that was so old it was still made in the USA (white and red label). I bought it just as a curiosity. What's the quality like on those? I also saw some Katrina bottles, and it was cool seeing them IRL after seeing pics on here. Anyway I am a young Padawan in search of further information. Please guide me.