The OWL probably contains upwards of 11,700 words that cannot be found in any of the four dictionaries used to update the Official Word List in 2006.  These words were found in earlier dictionaries and were grandfathered into the Second Edition of the Official Tournament and Club Word List.

   How did I arrive at the estimate of 11,700.  I combed through  the four dictionaries to see how many of the official two-five letter words were missing.  I came up with 1,262.  This is about 9% of the 14,084 two-five letter words found in OWL.  The OWL contains 131,097 words total.  By extrapolation 9% of the total words is about 11,700.

   Undoubtedly my count of 1,262 short words could be off by a little bit and my extrapolation  to 11,700  total words could be high or low by quite a bit,  since I don't really know whether a higher or lower percentage of long words would be missing from the current dictionaries.

   What I am sure of though is that there are a lot of strange words, legal in SCRABBLE games, that can not be found inany of the  current desk dictionaries put out by American Heritage, Merriam-Webster, Random House, or Websters New World.