I notice the catalogue refers to perloid inlays on some instruments and mother of pearl on others.
 
Is perloid a synthetic and MOP the real thing?

Yes - though since the catalog was published we've discontinued the pearloid inlay material.

I have a bass with pearloid inlays.  I wonder if it can be upgraded someday to the real stuff?

Sure, but we like to do it when we're refretting.