Weird marking on $20 bill. Is this normal?

[Unknown user]

I don't know if it was printed like this or if somebody stamped it on. I don't know much about this stuff so could someone help me. I've compared it to my other twenties but none of them have the same markings.

 

[Mackaydon]

Welcome to Treasure Net !!
Mark was placed there after issuance.
Don....

 

[Unknown user]

Thanks, i appreciate your response.