The site I found it on just says from the 50's. Here is a link to the site. They have the rest of this catalog as well as many other old and forgotten hardware store's catalogs. http://www.roseantiquetools.com/id42.html
The first three dates I just saw was 2-25- 59, 3-26-59 & 7-15-59.
So who made bikes for Keen Kutter, because I have a Monarch that looks like the tank bike on 7-15-59 page. How much would a Keen Kutter bike bring in todays market?