I have been a collector for about 13 years and have a couple of books to help guide me along.  I found that there are only a couple of books on Pyrex and one is The Unauthorized Guide.  But the first one is really a great guide.  Did you know that the yellow tint in the old clear Pyrex was from the arsenic they put in the glass to make it stronger?  One of the first applications of Pyrex was the 200 inch glass disk for the Hale telescope in the California Institute of Technology Observatory on Mount Palomar.  They use Pyrex glass in the test tubes, funnels, etc. at the lab where my husband works!  There were four plant locations in the U.S. that manufactured Pyrex.  I also have peices that were manufactured in France and England.  Pyrex did make items to use on the stovetop.  It was the Flameware  brand Pyrex.  I have glass skillets with detachable handles.  You could have a set of 3 skillets or pots and use only one handle for all three.  Virtually all Pyrex pieces are marked with the Pyrex logo.  Even the lids and handles.  In my book, it shows about 23 backstamp trademarks, but I think there are more.  One of the earliest was just stamped on with (some kind of an ink stamp?).  A lot of those peices are hard to identify because that kind of stamp would wear off easily.  And finally, I have found a casserole bowl that has a distintive RAISED design on it that I have never found in any book.  It is very unusual and has the popular pineapple motiff on it.  Hope that the Pyrex Collectors out there enjoy this little bit of info.  I love Pyrex and consider myself a "Pyrex Diva".  Thanks for checking in .