Edward,
IIRC...I think the Mauser folks have indicated in the past that you would expect to see BW grips on a '41 byf in the u- or t-suffix block and later.
This is a good discussion from the past on the LF :
http://forum.lugerforum.com/showthre...light=BW+grips
This discussion ran over on Jan Still's gun boards. It is an old thread so many of the photos are expired...but it is still an informative read :
http://luger.gunboards.com/topic.asp...ms=black+grips