Japanese Dragon box question about factory and construction

Hi all,

I'm wondering if anyone knows what company ZU is (or was) in Japan, approximately how old the piece is, and what the red material under the metal is? The material feels like Bakelite and looks a bit like imitation cinnabar. Thanks!

 

Here's a box by the same maker.
https://www.worthpoint.com/worthopedia/antique-zu-occupied-japan-ruby-red-253019155
Maybe will help date it as theirs is marked made in occupied (1945-52) Japan?

 

Thanks!