On 27 May, 07:44, Vet Tech wrote:

OK, I did the magnet thing and there was no attraction and going by
the weight, it feels like solid brass.

Watch out for brass over diecast zinc too.

For Screwfix I either check in the shop first, or I buy just the one
of something before buying a batch. They mix solid brass and brass
over zinc, yet describe them randomly in the catalogues as "brass",
"brassed" and "polished brass finish".

Not many castings (like doorknockers) are going to be brass on steel,
i.e. magnetic. That's more likely for things that are pressed from
sheet, such as mirror plates and lock escutcheons.