I have 4 Louis Cardin enamel on copper pictures dated 1978 and one of them has the number S694 on the back. It was certified and warrented by the Collector's Guild in New York to be an exclusively commissioned original. It also has the number S694 on the back. These pictures are of 2 girls in various poses. The one I'm looking at is a girl in red with a red umbrella and a younger girl in yellow picking flowers. Please tell me what they are worth.