Joe, here´s a copy of the e-mail I just got from the former B-17 engineer:
Roman...It appears to be the label that was attached to the selector gun switches on the Sperry Upper Gun turret....also could be the same for the lower ball turret as both were by Sperry.
Each gun...Left and Right had a selector switch which allowed the gunner to select either one or both guns to fire.
Not me...a friend of mine in the woods 6 miles away from my born town.
Most of the parts like that ended up here: http://www.ww2aircraft.net/forum/aviation/august-29-1944-museum-sanov-czech-republic-9882.html
Attached the pics of the particular a/c where this particular label hanged once...
It belonged to 99thBG and the it was trasferred to 2ndBG...
There was only one survivor...and I´m in touch with a nephew of a tailgunner. He should visit me in next years...