Paul,
Did a little online searching (it's slow here at work today

) and discovered the following information on ALCOA.
"The first was Alcoa. The Aluminum Company of America’s factory south of Knoxville, Tennessee, was then the largest aluminum plant in the world. Months before Pearl Harbor, as war loomed, defense experts realized how important aluminum would be in building an air force—especially one with the 50,000 plane-strength demanded by President Roosevelt in May 1940."
Unfortunately it may be difficult trying to identify what the part is for and what type of aircraft it went to...even with a picture.
John