... "what makes this chip so rare?"

Item: RARE, SAN JUAN PUERTO RICO CARIBE HILTON $1 CASINO CHIP (220035219292)

Response is as follows;
"I got this chip over 25 yrs ago when I lived in Puerto Rico. Last time I went to the Hilton 7 yrs ago they were using the regular chips. Have you seen this kind around?
That's what makes it super rare!!"