The symbol you're talking about was actually revised in 2013 to be a solid triangle around a number instead of the arrows: https://web.archive.org/web/20160126

The symbol you're talking about was actually revised in 2013 to be a solid triangle around a number instead of the arrows: https://web.archive.org/web/20160126213345/http://www.plasticsindustry.org/AboutPlastics/content.cfm?ItemNumber=823&navItemNumber=1125 https://web.archive.org/web/20160126213345/http://www.plasti...