I did a search and found this;
Crash in Destruction Bay
http://www.advrider.com/forums/showthread.php?t=371650
It is easy check which forks you have courtesy of the composite pic from squarewheels. The only known failures are the old style
http://www.advrider.com/forums/showpost.php?p=7633376&postcount=92
The forks on the left are the old type, the forks on the right are the new type. Both have the same BMW Part No.
The interesting part is we are not sure when the new type were introduced into production. Initially it was thought June 2003 but we now know of one machine built December 2002 with the newer style strengthened fork legs.
Thanks to the posts here we seem to have narrowed the changeover to Oct 2002.
You can check the production date of any BMW by decoding the VIN and there is a handy web site available to do so.
http://www.bmw-z1.com/VIN/VINdecode-e.cgi
It would be of assistance if people could post the results into this thread to narrow the production range of the machines with the earlier casting. Only post the production date and which type of casting the machine has
It would also be prudent for owners of machines with old style castings to refer any concerns they may have to BMW to satisfy themselves of the safety of these castings.