A one-shot provision point mechanism with money-back guarantee and proportional rebate of excess contributions is tested in an induced value framework and in experimental environments chosen to mimic field conditions. The results show that this relatively simple mechanism is empirically demand revealing in the aggregate when used with large groups of students who have heterogenous valuations for the public good. Approximately demand revealing behavior was obtained under three alternative information conditions. These results are an important step in the design of a mechanism simple enough to allow field applications, but capable of efficiently providing public goods through voluntary contributions.