Sports shirt with sewn compartment in pocket

[Espee]

I believe it's Arrow that is selling "Heritage Twill" sports shirts, a lot of them in what I'd call autumn colors. I noticed a seam dividing the pocket vertically-- making a space just about big enough for a medium-long pencil. And at the top is a mock buttonhole. There's no button...
So, what was the deal with the shirts they're apparently trying to emulate? What was carried in that compartment? Was there a button to secure the item?

 

[carldelo]

I imagine the pocket is meant for a pen, perhaps with the metal clip of the pen passed through the buttonhole so it can be seen? Just a thought...

 

[MB5]

I believe carldelo is correct.
It sounds like a variation on this that is likely easier to make.