I found a circulated blank canvas, seems like it was missed when in the striking process. It is a unstruck penny. What is the value?
It's your coin. I haven't seen it. Zinc cents replaced 95% copper cents 29 years ago so I assumed the unstruck planchet you found in circulation was a zinc cent. If it is not I apologize.
Balance it on your finger gently and lightly tap it with another coin. If it rings, (very distinct you should know right away), then it's copper. If it just kind of "thuds" it's zinc. I'm just going to hazard a guess and say a copper one won't be worth much more, if any, over a zinc one. But I'm with Hobo on this one; it is most likely zinc.