Damn it, I hate giving away secrets, Oh I can't believe I'm giving this one up. BLAH BLAH, any way Mike Sigel told me years ago that he only uses Lepro's, and he's only found one way to tell good from bad, sand the back of the tip, and the dark one's are the good ones, sand 50-100 and you'll know what I mean. That is why at this moment I have 50-60 good lepros on hand.
For those about to post, what about humidity, now you've taken the coating off and the atmospheric conditions will get to them, well that's why there are air tight containers/bags.
You do have to have a discriminating eyes/good eye sight/ attention to detail. My brother say's he can't tell most of the time unless it's night and day between the color. I can.
Darkest are the med. firm(the one's most people are looking for)
Dark are Med. very good tip, needs trimmed once or twice, plays great, shouldn't use for breaking
light chocolate brown, Meduim soft tip, good tip for spinning whitey, some mushroom alot, some not so much.
and when they start getting lighter in color 99 out of 100 are crap from hear. They seam to tear apart very easily, Rotten is the correct term.
The bad one's can be used for experiments such as milk duds, soaking in super glue to make a break tip, soaking in budweiser, alcohol, or putting on the cues of people I don't like:kma:
I also use these tips to replace the tips on house cue's at the local Ymca, my charity work. and I suggest you other cue repair guys who can retip house cues to do the same, It's a great thing to do.
EDIT: The only 2 exeptions to this I have found is:
#1 old lepro's anything that has been sitting around for awhile, how long? depends, we set up and do repair at quite a few tournaments every year including national tournaments now, so we put on countless amounts of tips each year. So we buy 4-5 boxes of lepros each year and maybe sell 50, the others I donate.
#2 when I rough the bottoms of the tips and if they are shaggy, or leather seams to tear, doesn't matter the darkness these are also bad.