I have the same problem with my 221. I have a collection of 3 original Rotary boxes with many different feet and accessories. I am in the process of trying to find out which goes with what machine. I too have a box similar to yours. I don't know which originally came with the machine. I am still trying to sort and label each. I too must have a feet fetish for my machine.
I also have a brother, not an older machine, that I organize my feet in a similar box.
As far a cleaning the feet, I have not gotten to that point. But when someone has a way of cleaning these feet please let me know.