Broken piece of tread. Wher it came from?

[dinikin]

While working on my 86 merc found this piece of broken tread, mathches the color orthe block or part of it. Plann on taking and cleaning carbs in a week or two.
It is kinda of a long shot but just thought I'd ask


http://www.flickr.com/photos/10571613@N07/912915375/