I remember button fly 501’s in the 60’s and 70’s.
The zip fly, as I recall, was started to promote Levi’s on the east coast. Must be they didn’t think we could figure out the buttons.
For years the genuine button fly 501’s were a western US item.
Levis 505. In the 70’s in Australia that was all that was available. At the time, I was not aware of the significance of the number. They were just Levis to me. Dark blue, rigid denim, slightly tapered leg and zipper fly. I know most people love the old worn out faded Levis but I love the feel and smell of the stiff rigid new denim. Unlike most other clothes where you can forget that you are wearing them, when you are wearing a stiff new pair of Levis you are always aware that you have them on. They make me feel horny 100% of the time.