I have recovered files looking like this from both my grand father's 
tool box (left in a damp shed) and from material from archaeological 
sites (prehistoric to historic). A X-ray and/or metallographic 
examination usually confirms the identification.

Chris

On 23/06/2011 18:18, Evans, Lynn (DNRE) wrote:
> I have a mystery artifact: iron, 13.5" long, bent up on one end, the hooked end is square in cross-section, tapered end is more rounded; found in a newly plowed garden plot in Mackinaw City, a little over a mile from Michilimackinac, only known historic use is pasture, a clasp knife blade and a hollow artillery shell (both compare favorably to Michilimackinac finds) were found close by
>
> Photo posted at www.flickr.com/photos/64404343@N02<http://www.flickr.com/photos/64404343@N02>
>
> Any suggestions much appreciated
>
> Lynn
>
> Lynn L.M. Evans, Ph.D.
> Curator of Archaeology
> Mackinac State Historic Parks
> P.O. Box 873
> Mackinaw City, MI  49701
> 231-436-4100
> [log in to unmask]


-- 
Chris Salter
Senior Analyst,
Oxford Materials Characterisation Service,
Department of Materials,
Begbroke Science Park,
Sandy Lane, Kidlington,
OX5 1PF