Standard Pre-Flag Blurb
Pre-Flag and Post-Flag are the same. I can prove it by selling you one of each for $30 per cube. They have been stored in the same room since purchased withing a year of each other. People who think that Pre-Flag is in any way different need their heads examined. I used to, and still do, throw away chalk that has become gummy due to exposure to the elements and builds up on the tip, cueball, and table like Kamui. That crap is junk. Blue Diamond is where it's at.
I wrote this Standard Pre-Flag Blurb as a brief overview of the entire situation...
There is a noticeable difference between older Master chalk and today's Master Chalk. The people who observed the difference initially, say they noticed it in the mid to late '90's. The flag was added to the label after 9-11, 2001 by Tweeten as a patriotic gesture. So there is not even close to a perfect correlation between the change in the chalk and the time frame the flag was added. And they still make "non-flag" labeled chalk today, I believe for foreign markets. I do think it's an unfortunate misnomer to call it "pre-flag".
A lot of people can tell the difference using this chalk, myself included. It is definitely different. It's grittier, holds on the tip better, less miscues, less cast off, and lasts longer. Tweeten says they made no change to the chalk itself, just the flag added to the label. Hence it became, and still is, a controversial issue. My theory is that something inexplicable changed in their formulation, ingredients or process. Hey, $h1+ happens.
The change in the chalk has no correlation to WHY the flag was added to the label and a very imperfect correlation to WHEN the flag was added. It definitely can be hard to say for sure that you are getting the real deal until you actually use it. If you want to buy "genuine pre-flag", try to ensure it was made before 1995-ish if you can.
For what it's worth, today's Master is perfectly good chalk. It's a matter of perspective. If you use center ball or minimal spin, you probably wouldn't see any difference from chalk to chalk in terms of playability. If you use extreme spin, I think you will miscue less with better chalk.
You can find more info about "Pre-Flag" by searching the AZ forums for "master" "chalk" and "flag". Here's one thread to check out...
http://forums.azbilliards.com/showthread.php?t=126352