Why do the patents on google patents contain 's1' after the patent number
e.g., http://www.google.com/patents/USD678656
USPTO doesn't seem to have S1: http://patft1.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=D678656.PN.&OS=PN/D678656&RS=PN/D678656
It is only on the end of design patent numbers. The letters after a patent number are a publication kind code. There is an international standard WIPO ST.16 for them but it seems to be special-cased in its use in various countries. That standard and a page on the USPTO web site:
says design patent publications in the US have a kind code of S. I found one other document that shows S1 or S but it looks to me that S is correct.
I see on a google page explaining the format of their XML information that the kind field is two characters and that S1 is for design patents.
