Anyone know why they have these various systems?
Fly: Zipper vs. buttons
Fastener: Button vs. clasp vs. clasp with set-back button.
All I can say is I’ve worn Levi’s 501 almost exclusively since the early 80’s and I’ve never been “caught” in the button fly.
That’s all the reason I need.
“Button up your overcoat and fly…”
I’m coincidentally researching a story on denim (see my thread on Soviet blue jeans http://boards.straightdope.com/sdmb/showthread.php?threadid=176169 ). The 501, with its button-fly is, as all the ads claim, a true original. The 501 was established back in the late 1800s (post gold rush … we all know the Levi Strauss canvas jeans story … ), and it had a button fly back then. LS & co. recently (the last decade) bought at auction a pair of 1890s jeans that were found in an abandoned mine shaft. You can clearly see the impression of the fly buttons through the front flap. It’s actually rather disturbing how completely modern the jeans look.
So the button fly was the first and only option. The zipper came later.
And I’ve worn zippers for the same length of time, and I’ve never been “caught”, either. I’m not sure how it would even be possible, if you’re wearing underpants. On the other hand, a button fly will never come open of its own accord.
Actually, most of the button-fly jeans have had the buttonholes wear out to the point that they wouldn’t stay buttoned any more, and the pants were useless from then on. I’ve only had one zipper break on me, and I’ve never gotten caught in it.