Control Serial Number: Edition 2 applies directly to all instruments.

Edition 1 : 1st May 1990 : 81531-90011 : E0590

1st September 1990 : 81531-90011 : E0990

Edition 2 : 1st September 1991 : 81531-90011 : E0991

1st September 1992 : 81531-90011 : E0992

1st December 1994 : 81531-90011 : E1294

1st July 1996: 81531-90011 : E0796