Thanks to my friend (http://japan-saito.blogspot.com) I was informed of archeological finds in Japan which show Islamic pottery dating to 768CE.
An English article can be found at:
http://search.japantimes.co.jp/cgi-bin/nn20090705a9.html
Japanese articles can be found at:
http://www.asahi.com/national/update/0703/OSK200907030157.html
http://jp.reuters.com/article/kyodoNationalNews/idJP2009070301000680
etc…
I will write more once I know more.
Interesting link. The one discovered with Chinese writing is from the Tang Dynasty.