I'm not sure of the process, but these "mats" were sold or given to Colt authorized dealers so that they could have local advertisements printed. I have an entire Colt catalog of this sort of stuff. I'll take some photos in the next couple of days to show you what they were like.
Here are some photos from the catalog. From the guns illustrated and the Colt business address (pre-zip code), it appears to be from the early 1960's. These were sent to dealers in order to aid them in advertising in local media (newspapers and television at the time).