You have already probably resolved this, but I looked up your surname in the Register of Swiss Surnames in the Historical Dictionary of Switzerland. It is online and can be translated to English. Your initial said Mohlin, not Rheinfelden, Mohlin is a very small but old area. My family is from the same town. Nothing came up for the spelling you listed so I listed the surnames and a Lichtin came up. If this is your family, it was coded a. which means the family has been Citizens of Mohlin from before 1800. I checked the name for Rheinfelden and nothing similar came up. (Rheinfelden is the District) Swiss citizenship (if you have it follows you from your "home" town). You probably already have this under control, but it is easy to check on line and hey--our families were probably neighbors!