.stl (model/stl) file getting an unknown icon

This is Nautilus 42.1.1-2 and papirus-icon-theme 22020508-1 - this install is a few days old.

My .stl files are getting the grey question mark unknown icon

Looking through Papirus’ git,

/usr/share/icons/Papirus-Dark/16x16/mimetypes/model-stl.svg exists

I also find a command to run;

gio info -a standard::icon

standard::icon: unknown, model-stl, model-x-generic, unknown-symbolic, model-stl-symbolic, model-x-generic-symbolic

So why the unknown assumption? I’ve only got OpenSCAD & Cura on this machine at the moment, if that makes any difference.