The Courier typeface, designed by Howard “Bud” Kettler, has an interesting history which has been discussed in other places so I won’t cover that here. But, a question that sometimes gets asked is why the Courier New font that ships with Windows is so thin?
The Courier typeface was originally designed by IBM for their typewriters. According to Monotype, the original outline data that they used for Courier New was digitized directly from the golf ball of the IBM Selectric.
The raised image of the golf ball is designed to be thinner because when the image strikes the paper there can be significant spread of the ink on the paper.
Because the Courier New outlines are so thin, we had to make a special case when we displayed the font with ClearType and actually “thicken” the font to make it readable. Without ClearType, the outlines are being “rounded up” to one pixel.