I love when stuff like this happens. While searching for 1999 Teleca (테레카) singles to buy I also came across these gems and had to buy what I could. I don't know if an entire sample set was released but I found of eleven of them so perhaps we can presume so? Nothing was different on the front of the cards.
What I found interesting was one of the samples had "스포즈서울" (SportsSeoul) on the back of one. So I am unsure if an entire set was released with this stamping.