Not slags, they look like opaque based gaming marbles IMO. Slags are transparent based (i.e. blue, green, amber, red, etc) w/ white opaque swirls running through them, here are a few links for you to ponder JJ, have fun
MARBLE CONNECTION LINK :: https://marbleconnection.com/search/?&q=slags &type=forums_topic&quick=1&nodes=20&search_and_or=or&sortby=relevancy
AAM LINK :: https://www.allaboutmarbles.com/viewtopic.php?f=7&t=43796&p=322493&hilit=slags+definition#p322493
AAM LINK :: https://www.allaboutmarbles.com/viewtopic.php?f=5&t=21536&p=170931&hilit=slags+definition#p170931
AAM MULTIPLE LINKS :: https://www.allaboutmarbles.com/search.php?keywords=slags+definition