I have a feeling that it might have something to do with Christianity. I never even thought of that. I was very perplexed when I pulled it out of the ground.
I think it is a neckerchief slide for a boy scout/girl scout/ or some type of troop or pack. There are troop number 777 in many states. The links below are just the first two I found on Google. In what state did you find it?
http://www.magnificentsevens.org/uniform.html (Note a neckerchief slide is the 2nd item listed.)