In Germany we've got 'Unze' (ounce) which is defined as ~30g which we only use when talking about precious metals.

What we do use is 'Pfund' (pounds lbs) which is defined as 500g.

I am amazed the nations of the world actually came to an agreement about what to use as base units and I can't even fathom what shit show it must've been before that.

I live a 30min drive away from the Netherlands and your ounce is already 230% more then my ounce.

But "hecto" (gram) is not used as a synonym?

No it's not, at least not in the Netherlands.

In Germany the short "hecto" stands for "hectoliter", when ordering larger amounts of beer.

This is commonly used in Italy modified in the form "etto"