The insignia you are describing is, I believe, the regimental crest (or Distinctive Unit Insignia - DUI) of the 50th Infantry Regiment of the US Army. The critter in the center stripe is a dolphin (I agree, it looks like a dragon, but it's not) representing the city of Syracuse, NY where the regiment was originally organized. The symbol in the canton is a totem pole, taken from the DUI of the 23rd Infantry Regiment, which provided the cadre around which the 50th Infantry was formed. The pale and wavy edges of the blue stripe represent the regiment's occupation service in the Rhine Province of Germany after WWI.
Campaigns: WWI; WWII - Normandy, Northern France, Rhineland, Ardennes-Alsace, Central Europe; Vietnam - Counteroffensive Phases III/IV/V/VI/VII, Tet & Tet/69 Counteroffensives, Summer-Fall 1969, Winter-Spring 1970, Sanctuary Counteroffensive.
Hope this helps.