WMF Backstamps, Condition Issues, and Identification
Because I'm filling out an old set of WMF Cromargan stainless, mostly via eBay, etsy, and Replacements Ltd., I've had need to question sellers about certain issues, namely, the backstamps and condition of the pieces.  I created the images on these pages to make it easier to discuss these matters with other buyers and sellers.
In addition to documenting the identity of the manufacturer, the backstamps have a bearing on the place and time of manufacture, which, along with condition, have a bearing on the desirability and, hence, the value of a piece.  I would encourage anyone selling WMF pieces online to please include an image of the backstamp. 
WMF Backstamps
As much as I love my WMF stainless, like all stainless it is subject to pitting if mistreated.  While scuffs and scratches can usually be buffed away, dents, dings, and pitting cannot be repaired, so these dramatically affect the resale value of used pieces.  For images of some types of flaws, please see this page:
Stainless Condition Problems
Discussion here is aimed primarily at WMF stainless made in Germany in the 1960s and 1970s, but other information is added as I stumble across it.  Gradually, WMF began manufacturing at least some of its products elsewhere, first in Europe (e.g., Sweden, Denmark, Spain, Italy), then in Asia (e.g., Korea, Vietnam, China, Taiwan), and elsewhere.  This geographic shift has placed a collectors' premium on items manufactured early on in Germany.
In the "by the way" department...

WMF does not stand for "William Fraser," it is the acronym for Württembergische Metallwarenfabrik, which in English translates to Wurttemberg Metalware Factory.  The company was founded in 1853 Geislingen an der Steige, Germany, by Daniel Straub (see also entry at Wikipedia).  The AG in "WMF AG" stands for Aktiengesellschaft, which is roughly equivalent to a U.S. publicly-held corporation (e.g., our "Corp." or "Inc.").  This mis-interpretation of the WMF acronym was an error if not made by, then at least followed by Page & Frederiksen in their (1998) book, Stainless Flatware Guide, an error that has been widely promulgated ever since.  The Fraser in "Fraser's WMF" was Gordon Freeman Fraser, who founded a retail housewares store in Berkeley, CA, in 1947.  WMF bought Fraser's making it a division of WMF, and Fraser's Ltd. became the distributor of its housewares.  Gordon Fraser eventually moved to Geislingen where he played a major role in the development and marketing of WMF products.  Upon the death of Gordon Fraser in 2005, "Fraser's" ceased to exist under that name, and WMF products are now distributed in the U.S. by the WMF Americas Group.

"Cromargan" is WMF's trademark for stainless steel, registered in 1927.  While the web site states the trademark stands for 18/10 stainless, I have seen WMF pieces stamped "Cromargan 18/8."  I suspect WMF simply no longer makes 18/8 stainless, which would explain why they don't mention it on their current web site, but clearly they did once make it.  The numbers stand for the percentages of chromium and nickel, respectively, in the steel.  Nickel is expensive, so 18/10 stainless is likely to be more expensive than 18/8, but functionally there is little difference.  The chromium is what makes steel rust free ("rostfrei" in German); the nickel is what gives it a silvery luster and resistance to acid.  Because steel containing nickel will not hold a good edge, knife blades are made with 18/0 steel, which you can detect because the blade will be magnetic, while the handle won't be.  Obviously, this applies only to "hollow handle" knives where the handle and blade are two separate pieces, not to "solid handle" or "flat handle" knives where the handle and blade are one single piece of metal.  The lack of nickel in the blades is also the reason knife blades are so prone to pitting and corrosion.

While stainless steel doesn't rust, it is not indestructable.  To avoid pitting your stainless, never soak it and don't leave acid foods (e.g., tomatoes) sitting in it.  Especially, do not soak or even wash it in chlorine bleach and/or in contact with other metals, such as silver or aluminum.  To avoid getting "rubs" on your stainless (and marks on your dinnerware), wash your stainless by hand, not in the dishwasher.  If it's expensive stainless, like WMF, handle it as gently as you would silverware.  A good, mild polish for satin stainless is WMF's own Purargan; a stronger polish, suitable for glossy stainless is Wenol.

With regard to my WMF Cromargan pattern:  LINE.

My pattern, LINE, which I first purchased back in the 1963, is now one of the more expensive WMF patterns to replace a single teaspoon will set you back $109 at Replacements Ltd.!  There seems to be a tendency for sellers to wish/hope what they are selling is LINE, so several similar WMF patterns are often mis-identified as LINE.  The most common mistake is identifying pieces of LAUREL as LINE.   I'm in the process of preparing a page to help with the identification of LINE.  I'm also preparing a page illustrating all the known pieces of LINE and pieces of vintage WMF Cromargan holloware.

Other internal links:

WMF vs. Alessi Stainless Steel Wire Basket