Individual States interpret financial transactions and contracts differently. So, just as SOL will vary from state to state, so will interpretation on type of account.
I'm not sure that there is mutual exclusivity between an "open ended" and "written contract" since you do have a written contract which states the terms of use, even though the account is revolving.
NFCU classifies it's NAVcheck LOC as an "open ended" credit contract. When you apply they actually send you a written note and contract which you must physically sign and return...whereas the credit card you can apply and be approved online and the only "signature" you make is on the back of the card or with the merchant, which generally states on the transaction, "I agree to pay the charges according to my cardholder agreement" which constitutes a signed contract both for the credit agreement and the transaction.
Usually the card and its terms state "use constitutes acceptance" of the cardholder terms. Further, when you use a credit card, the fact that financial consideration with promise to pay meets the litmus of a contract. A contract requires two parties, a meeting of the minds (terms and agreement), exchange of consideration, etc.
