It is a photocopy of a drawing made from the original painting which was in the possession of Dr. Nathaniel Emmons. The original was destroyed in a fire. In the description on the back the name is spelled as Edmons. There was a crusader coat of arms about 1440 as found in an index. I have no idea to whom or how this coat of arms was presented to an Emmons.
Further research is needed.
If anyone has any information, please let me know. My thanks to L. Emmons for this information. It is a popular misconception that the word 'crest' describes a whole coat of arms or any heraldic device. It does not. There is no such thing as a 'coat of arms for a surname'.