These are 70mm x 70mm slides, please note they don?t have a dark line through them. That?s because the viewer I?m using is for 35mm slides. These slides are piece of film between to thin pieces of glass Could be late 1950s or early 1960s, not quite sure. Always happy to answer any questions if I can.We will combine shipping, especially on small items it cost the same to send multiples as it does to ship one.