Adoption Certificate

I found this almost 3 years ago amongst my baby records and when I approached my mom she told me that I was not adopted and my sisters were just playing a joke on me. My sisters denied having any part of it and I know they would of admitted it seeing how insane it made me. Can anyone tell me if this looks like a legit document generated in 1980 in Texas. It looks like just a souvenir certificate, similar to the ones you get at the hospital when your child is born. The Texas seal is raised and it was signed by the governor (which I thought was odd). Thanks!