Removing the final screw in yellow, the brass ring can be lifted out of the barrel.

Then all of the aperture blades can be removed from the barrel as well.

Some care should be taken when handling the blades to avoid bending them. Blades may be stuck together from oil.

All pieces of the aperture assembly should be oil free. Clean all parts with 99% isopropyl alcohol.

A film canister makes a good vessel to place aperture blades into for cleaning.