:::: There is an infamous "A 800" mark on Italian silver that usually turns out to be silver-plated, but there are some cases where it is actually 800 silver purity, I believe this is correct, it is sometimes 800 silver but usually it turns out to be silver-plated base metals. ::::::::::::
It looks like A 800 is raised from the surface of the plate, i.e. it is stamped on the plate itself.
It is unlikely to be Italian, usually the "infamous" Italian mark is Arg. 800 or Arg. 1000.
I think it is Belgian, probably solid silver.
Test it and let us know.