​Small metallic (shiny plastic) disc glued to the bottom of 2 insulated water bottles (different brands).

I bought 2 insulated water bottles from 2 distinct brands in 2 different stores, both had the barcode sticker at the bottom, when I peeled them away, I found this metallic disc on both (it feels more plasticy but can’t fully tell). In one of the bottles, the disc came off with the barcode sticker and I threw it away, but it stayed on the second bottle. My first guess is it could be an anti-theft tag of some sort. It’s just interesting that the disc fits perfectly in the indented circle but is relatively easy to remove.