I have two lenses that use the same old Copal 3 shutter. (Xenar 210 mm f/4.5 and Telomar 360 mm f/5.5.) I don't want to carry both Copal 3 shutters for these two lenses in my backpack due to weight and size. I want to carry just one mounted lens and the elements for the other lens; when I need to use the other lens, I will exchange the elements. How can I safely carry the elements in my backpack? I want to protect the threads and the glass without devoting too much pack space.
A related question---is there a name for this particular kind of Copal 3 shutter? It's threads are different from a modern Copal 3.