Any idea what this is?

Friend of mine unearthed this from his daughter's attic.
Dejunking the rubbish gathered over the years.

Markings are CTCO S406240 and S1054B (last digit could be 3 or 8 though)

It’s heavy.

No crows foot in evidence though

Thanks

 

Bryan,
All I could find is a French company called STCO in Lyon selling promotional items.
Stefan.

 

I was thinking more along the lines of a scientific vacuum semi sphere.
Regards
Tom