ISO9000 CAD numbering

Hi,

I have a general question about devising a numbering system for CAD 
drawings. My engineer insists that every project we work on must have a
set 
of unique drawing numbers, even if the drawing is one from a pool of 
standard components. To me this seems counter-intuitive; if a drawing is
of 
a standard part (albeit one that we get manufactured) then it would make 
sense to me to leave the number unchanged. Otherwise we have 2 drawings of

the same part that have different drawing numbers.

Does ISO9000 state absolutely that drawing numbers must be unique, or is
my 
engineer over-interpreting things?

Thanks,

Gerry