Russia 1959 - Defect? (No Pun Intended)

I was scanning some Russian stamps to sell when I saw what I took to be a tear in the corner of this 1959 stamp of the statue of Tchaikovsky in Moscow. But checking the back of the stamp, there is no tear.
Is this a plate defect? A fold in the paper when printing (there is no crease on the back of the stamp)?





This is a low value stamp. Does this add to it's caché? Value?
Reason to keep it?

I can see the perf tips of another stamp.
Someone glued it the corner to repair a damaged stamp.

Well, Alan, I was going to strongly disagree with you, but then I scanned the back and saw things I couldn't see under my 10X loupe.
I figured the overlapping perfs that you saw were just chads that had not come out.
But the scan showed an angular thin in the corner in question.





Then when I held the stamp up to the light I could see it much clearer. It appears in the photo as a white shape.



So I do believe you are correct. A repair. Which begs the question, why would anyone go to the hassle of repairing such a valueless stamp? Unless of course the mistake that caught my attention was done on purpose to make collectors like me think they'd found something rare.
Almost, but not this time! Conspiracy everywhere!
Thankyou Alanl.

Too bad James! I think it`s just a case of someone
having 2 defective stamps and trying to make one stamp
from two for their collection. Not a very advanced
collector.

It is a repaired stamp. You can either put it in watermark fluid or hit with filtered UV lamp and the repair should show more clearly.