Is there a way to EXCLUDE coins made of a certain metal(s) from the search results?

When I search for commemorative coins on Numista for a given country, I may want to exclude Silver coins (there are a lot of them!)
I may not know what metals I want, but I sure know what I do NOT want )

In Google (and other search machines) there in an option to put ' -Silver ' in the search prompt: the '-' in front of Silver indicates that the links with the word 'Silver" must be excluded.

May be there is a way of adding the '-' option to the Advanced search.

Thanks!

Sincerely,
Chaosharvard

You can put "non precious" into the "metal" field.

Cita: "numinis"​You can put "non precious" into the "metal" field.

​While this may work for the specific example, it would be slightly more tricky if say I wanted to exclude copper coins.
Ideally, if coin metal was implemented to be a predefined parameter (i.e. when adding a coin, people would select from a drop-down list), search could support multi option checkbox. But I appreciate that's not the case.

Cita: "numinis"​You can put "non precious" into the "metal" field.

​Thanks, Numinis!