I recognize those from my steel fabrication days, black and decker wildcat, a very heavy grinder that would not give up easily. Unimaginable amount of boxes of grinding disks they would eat up.
Edit to add... This made me remember something funny, osha would announce when they would show up for a visit and when we knew they were coming we would put the guards back on the grinders and the guards were brand new because we never used them, the grinders were beat to hell and with the new guards on them well you just had to laugh