The parent specifically refers to holding it as cash (“under the mattress”), though. And of course, if you do put it in the bank 1923, there’s no deposit insurance for the first ten years, any possible bank might just go under in the first ten years…
The numbers I find are that some 11,000 out of 25,000 U.S. banks failed between 1929 and 1933 - the key words to search for are “bank failure” and “Great Depression”
