This because, only the most necessary articles were permitted to be manufactured.
A lot of magazines came out with do-it-yourself versions using unlikely materials to make your own brooches and necklaces etc.
Here some instructions of buttonholes, necklaces and brooches.
Also today this technic is still used, I think that these brooches are really beautiful...
on etsy: aaliciawedding's shop
Have a good day...