The Mylar was purchased from Richard Garner the owner of the Space Collective. The Mylar was used as part of the protective packaging of a consignment of cloth patches and metal lapel pins that were transported to the ISS. the packages were then exposed to the vacuum of space and spent 11 or so months attached to the exterior of the International Space Station, before being returned to earth.
The collection contains one of the patches, Collection Number TSM-010 which can be seen here
(A link at the bottom of that page will return you here)
The section is 50mm by 25mm and was purchased with the idea of incorporating some or all of it into a Space X Falcon 9 model that was under construction in 2021.
The piece was used to depict the insulation on the second stage Merlin engine of the SpaceX Falcon 9. The model build can be seen in the Space Models section of the website. Click on the link to go to SpaceX Falcon 9