Gilles: Very few a/c that were at D-Day would have used that series engine. Certain C-45's, UC-70's, UC-81's, AT-19's and UC-43's. By far the majority of the AN-3 series engines were used in various trainer aircraft that never got close to the front.
The data plate give you the exact designation, the serial number, contract info and various pieces of technical data for quick reference.