I have joined Jersey Archive. It costs @£30 p/a for unlimited downloads - registration cards, parish registers, hospital records, prison records... My father's maternal grandmother used her marriage certificate as id for her registration card, but this was inaccurately recorded. Jersey Registrar were able to find the actual certificate as I was able to give them a ball park date through 1911 census. All my dad's other relations' id details were accurate and I was able to find out a lot more about French and CI military service, occupations etc from the information given. My advice is to cross reference information and to check against the 1920 Alien Registration Cards (also on-line at Jersey Archive) as well.