Phil Anthropist wrote:

I can't believe that anyone would recommend using fine grade wet-or-dry
abrasive on an acrylic bath. Try Googling for acrylic bath cleaning and
acrylic bath scuff marks.

It really does work, Phil. I tried it out on the old acrylic bath
(still awaiting a trip to the dump) after the Natural Philosopher
posted his comment. I deliberately scored the surface with a stone and
then went about it with the wet and dry and the Brasso. First, it
dulled over and the scratches disappeared. Then I carried on with the
Brasso and plenty of elbow. After a while, the gloss finish came back,
exactly as I was told by Armitage Shanks.

Bruce