Yes, the box is the mystery!! But one thing, we can say it does not date as far back as 1930 - this latest post is one that is from that era - but the one from the mystery box is definitely a later piece than this, I don't think it can be form the 1930s. It just goes against the observed construction conventions. But you would be right to say there is no written proof of anything!!
These are certainly not rare awards at all, (yes, the one box is odd, I'd call it scarce if not rare....) - BUT the documents certainly are. i wonder why? I would think the documents would show up more frequently given the number of medals found. It would be useful to find mated medals and documents to help with placing dates to medal types. I know this is not 100% guaranteed, but it would be a start. Alas, it is a rare thing to find this situation!!
At some point, I will make measurements of the thickness of this medal compared to the others, again - not helpful yet - but it may be of value at some point - placing thicker, heavier medals within a timeframe, or possibly from a specific maker???