The original washers were leather.
Now that you mention it, I guess they were. I had assumed they were rubber with fiber, like the automotive hose.
Rim Locks are no longer needed. They come from an age when people (real men) regularly rode these bikes off-road. If you're running modern tires fully inflated, and never leave the pavement, then you will never need Rim Locks.
Did you weigh in on the debate in the other thread on this topic? I'm generally of the same opinion as you, and I shed my rim locks years ago, but after the one testimonial about a deflated tire coming off the rim, I decided to just clam up about it.