When I was a student, I had a reason to visit the San Francisco branch bank of the Federal Reserve. There were tellers in the lobby as I recall.
Just what do they do? Do they make change? After all, that’s one place that most assuredly will be able to break a $100 bill? Do they sell T-Bills or Savings Bonds? The webpage for the SF Federal Reserve Bank didn’t shed any light on the situation.
You answered your own question. The FRB sells/redeems savings bonds and government securities at those windows. I wouldn’t ask them to make change though.
The overwhelming majority of people have more than the average (mean) number of legs. – E. Grebenik