This little bag uses
The Interchangeable 3 Bag silver frame
by Ellen Medlock
The silver frame has loops where you can attach your strap with clip closures.
I had the silver clips and attached them to the silver chain.
You can purchase patterns, frames and ready made chains from the website here
A sleeve to thread the rod into is on the inside of the bag.
The lining folds over to the outside to form a piping.
In hindsight, I wish I had picked a different lining.
Below, you can see the rod removed.
It is very easy to thread the rod through the frame and the sleeve to change out your bag.
The fabric is wool felt, embellished with flowers and threads.