This is hard to explain so please bare with me and if you have questions to clarify, feel free to ask. 

I have received, since joining PBS, a number of books that have, um, speckles that are ususally, though not always, faint.  For the most part, they are on older books and so I attributed them to aging.  Since signs of aging are allowed, and I was planning on keeping the books anyway, I had no problems.  Now I have a WL book that was published in 2006 with these speckles.  Its really in great shape otherwise and I would like to post it.  But I'm afraid if I do, someone will interpret the speckles as stains and mark it with a problem.  Does anyone know what these are/how they are classified?  Are they a sign of aging and allowed? or was I wrong and they are stains?

They are probably called "foxing" I believe the term is. It's a combination of aging and paper & ink deterioration that causes speckles. I'm not sure how you tell the difference between foxing & mold, since mold is little speckle also! But, I think mold is white, and can be flecked off. Hopefully, someone will come along and correct or confirm this.

And these fleks are only a problem if they are mold. If they are not mold but simply a deterioration/coloring, no one should be able to give you any static over them if you post them.

Sherry, thanks for the quick response. 

In this case, the speckles are a faint yellow/orange color just like the usual discoloration.  They don't come off, the book does not smell like anything but book ( I love that smell ;-) ), and there are not signs of water or humidity damage.  Can I assume the problem is this 'foxing' and not mold?

Here are some photo examples of foxing      http://www.bookologist.com/cab/abu/y203/m03/bk0001/s03

Thanks so much Charlie! That's what it is, only better bc the foxing is much lighter, only on the page edges of the top of the book, and with just speckles none of those streaks on the book I want to send.