Wondering what the crescent shape stamped into the base of my chalet style art gl bowl means?

I have an art gl bowl, in the chalet style with a small crescent shape stamped into the base. Does anyone know what this mark means, and who the maker might be? I have searched online and can't seem to find this anywhere. Does anyone know of a website where I can get this information? I also suspect it is either vaseline or uranium gl, how do I tell? Thanks.