I've recently gotten around to resacking a pre-streamline lapis Duofold Sr. (all else that I could do to refit it having been accomplished earlier), and once I had it inked, I popped in into my pocket for a day on the town.

Hmmm....

Sheaffer snorkels fit.
Vacumatic standard fits.
Various numbered Parkers fit.
Wality 69L bloody fits.
But this blue behemoth barely gets the ball of its clip onto the fabric!

So, I now ponder-- did successful businessmen of the late 1920s have, literally, very deep pockets? Did depression and wartime rationing reduce once-mighty repositories to mere flaps of their former selves?

And more importantly-- how to I take my splendid pen out in the world without terror of it flying free?

In photographs from that period I've noticed that a lot of men carried pens with clips in their suit breast pocket. Perhaps that was cut deeper in those days. Maybe that is why Parker also made the Duofold in Junior and vest pocket sizes. Perhaps someone else will know more.

I've never had this problem carrying my flat-top Senior Duofolds in either dress shirts or the Hawaiian shirts I usually wear. While the latter are made for me by my wife, she's using a standard pattern so the pocket isn't enlarged. The dress shirts are store bought. I also have had no problem carrying my Chris Thompson replica Red Giant, which is quite a bit longer. The only shirts I know of that I have that would be a problem are some knit golf shirts I got from Walmart, as they have smaller than normal pockets.

The Big Red fits all my office shirts except the stupid ones that haven't got a pocket. That was fashionable a year ago :-(

T-shirts luckily don't have pockets. Who wants a pen on the weekend?

Bear in mind that the Giants were made in an era when the washer clip was an optional extra and the jack knife pens didn't come standard with a clip. Those pens with clips tended to stand out of a pocket leading Uncle George to design a clip that would keep the pen as low as possible........
And his pockets got deeper and deeper as a result ;-)

I've worn my Duofold Big Red (flattop variety) in my shirt-pockets before with no problems whatsoever.

In-response to the history of clothing thingo - Perhaps it was WWII. During the war, a lot of clothing was "cut down to size" - Any absolutely unnecessary fabric was removed to save cloth for...whatever. Perhaps tailors were forced to cut down on pocket-size?