The mintage numbers in the redbook should provide information on which quarters would be considered rare.
Look here as well, $$ will give you an idea of what's more rare / valuable. http://www.numismedia.com/fmv/prices/wshqtr/pricesgd.shtml
I think the ATB "S" are interesting with mintages of about 1.4 million. If they remain tightly held by collectors, then it's just a roll of coins you paid .35 a pop for from the mint. If they get dumped into circulation, then it's a rare find by roll searchers and become highly sought after. I love the dilemma. Too bad I probably won't live long enough to see it played out.
These prices appear to be assigned almost randomly and do not reflect the relative difficulty of finding nice clad quarters. By far the toughest is a nice XF or better 1969 and this is followed by the 1971. Look for well made coins with light wear and no heavy marks or corrosion. If you start a collection of them in one of the blue folders you'll quickly learn which ones are tough and which are easy. You'll also be able to spot varieties and always have a coin to compare it to.
Well like any guide, it's only a guide. I have used Numismedia extensively for a couple of years, along with completed auction prices at www.ha.com and www.ebay.com. I know of no better way to get a more complete up-to-date approximate value. These prices are based on what people are willing to buy and sell for, not how hard it is for you to find these coins in circulation. (I think that's what your suggesting?) If it takes me 5 years to find a nice AU 1969 quarter in circulation, but I can buy a TPG MS63 for a few bucks shipped, or a MS64 for $12.00 shipped, guess what, that's what it's worth, not 5 years of effort. IMHO, many of the low and medium grade quarters are probably not worth holding onto, unless they are special in some other way, like Type B reverse, DDO/ DDR, errors, etc.
Of course you're right. But collectors shouldn't think that this guide is in any way reflective of scarcity. I'd wager that you wouldn't find a nice attractive AU '69 quarter without looking through several hundred rolls. Even a nice XF will prove elusive. The '69-D has a lower mintage but it's far easier. Some of these dates are extremely tough and it's hard to figure why. The '73-D is another that's tough above XF-. These were common only 20 years ago but no more. The '69 has always been tough.
