Pretty slick and functional given the materials of the time. I wonder if it could be made to work today. I think adapting it to cards and cash would make it an awkward package, but maybe if you lay them out along the arm it could work.

Bronze is a VERY nice material. It's a shame it's actually too expensive to see much use in our modern consumerist lives.

It's also easy to steal

Not when it's a solid band around your wrist. Materials in isolation don't tend to have an inherent difficulty level of theft.