Good morning, pryan9;
A couple of suggestions for argus* C3 and MatchMatic C3 resources:
http://www.arguscg.org.
arguscg@yahoogroups.com (for sending a message to them)
or, just go to YahooGroups.com, and hunt for the arguscg Group.
And, you just missed their annual gathering in Eden, North Carolina. There are a lot of people there who are willing to share knowledge and help with repairs.
You have one of the cameras that did more than the combined efforts of all other 35mm cameras to make 35mm film the film format of choice for America back in the 1950s and 1960s. There were more than two million of them made during their production from 1939 to 1966. While many today look derisively at "that lowly argus C3." there is no denying the effect that their shear weight of numbers had on photography in America. It was "the people's camera." There are millions of people today who can say; "My Dad had a C3." Unfortunately, as with your grandfather, most of the original purchasers of these cameras are gone now, so much of the history associated with these simple cameras is being lost.
* By the way, that lack of capitalization is not an error. Normally it was written with a lower case "a" as shown.