BillP wrote:

When I cleaned it, just after installation, there was no evidence of any
chips. The chips are tiny and are about 7 or 8 mm apart on the side
where the bath is just starting to curve towards the bottom, about one
third from the end.



This location sounds like it may corresponds with the position of the
fittings for the legs under the bath.

It's not close enough to convince me though. Thanks for the input.
Dave