Oh my goodness, those markings are very similar to my Hyundai discs!
My Hyundai discs have the same sound wave mark on the underside of the disc, along with the “CDR UG 80” that’s on the underside too, along with a number that is opposite to the “CDR UG 80” mark.
Infact, the only difference between the disc is the number that is printed on the transparent hub is missing, and rather looking as though the text has been printed onto the disc (for example, the sound wave marking with the letters) these have been etched onto the disc, and they are much harder to read.
However, where the numbers are missing on the hub on the disc, next to it is some more numbers [including brackets] (09112101).
I noticed that you pulled that image from your Rare and Obscure media thread. OH MIGHTY PEPST, have I bagged myself some rare and obscure media?
(Side note; Hyundai seem to have no recollection of making these discs; I can’t find them anywhere. It seems like a classic case of plethora of discs that Hyundai have snapped up for next to nothing then sold on under their name )
Although having said that, from the small handful of Plasmon discs I’ve actually used, including Poundland-apt Signelex, EMTEC, and now Hyundai, not one of them have gave me problems