Thanks to Jonathan & Tedd, I think I can understand and get round the
problem which I'll describe as help to others.

The Delta RIP software is running on a PC with Windows NT which has it's own
Arial font.

As Tedd suggested, I wrote a fb app to print the complete chr set and
compared the LaserWriter output to the RIP output. Sure enough, the Mac blob
is ASCII 165 and PC plod is 183 (PC 165 is the 'Y' thingy).

So, when I go to print, it's interrogating the RIP and saying "Arial is
already here", substituting the PC version.

Unfortunately, I can't just dump the font off the PC as Delta software uses
it for screen display. However, my print driver can be configured to 'Always
download needed fonts' which solves the problem.

Thanks again lads.

Bernie