How that is done (metal or plastic) is usually a trade secret. The Crane Company, who produces paper for the US Dollar, won't tell how the security strip is placed inside the paper, but they will show plastic strips are 5 strips wide on a roll and slit into individual strips that are over several miles long as they go into the paper during the process . At that point of the process they stop any outsiders or cameras.

The paper comes to the BEP with the strip, watermarks, silk threads, and any other security devices in the paper. These rolls weigh in the tons. Every inch of the paper, like the notes, must be accounted for and any scrap is distroyed.

The partially visible metal strip, my guess is a corridated roller somewhere in the dewatering process of the paper.