The card has no copyright markings on it as can be seen in the links above.
United States Copyright Office page 2 "Visually Perceptible Copies The notice for visually perceptible copies should contain all three elements described below. They should appear together or in close proximity on the copies.
Note that it may still be copyrighted in jurisdictions that do not apply the rule of the shorter term for US works (depending on the date of the author's death), such as Canada (50 p.m.a.), Mainland China (50 p.m.a., not Hong Kong or Macao), Germany (70 p.m.a.), Mexico (100 p.m.a.), Switzerland (70 p.m.a.), and other countries with individual treaties.
{{Information |Description=Postcard photo of the Dry Gulch Railroad miniature train at Hersheypark. |Source=[http://www.ebay.com/itm/HERSHEY-PA-Chocolate-Town-Miniature-RR-Train-Old-Postcard-/330624733518?pt=LH_DefaultDomain_0&hash=item4cfac5114e#ht_12...