Where did you see the clover chip? This is the only one I've ever seen. I believe the white ring was added by USPC to designate it as a one time custom chip not to be confused with the normal tango chips

I bought this chip on eBay many year ago. As I recall (my memory is going fast), the seller showed bad pictures of the chip. However I was on it like white on rice. If anyone one was going to outbid me they were going to pay a small fortune. When I got the chip I noticed two other details. The color was pure yellow, not the darker more golden yellow of the tangos. Also the tangos have a reeder edge. The clover chip has a square edge and is a bit smaller. The last thing I checked was to see if the chip was altered by a third party. It was evident to me that the white rings were inset by USPC. Also it was clear to me that the clover with the clear celluloid covering was also original. The chip is as USPC made it. No alterations were made. My theory is that the Tango had the single chip made for a "special" customer since it would be considered a LUCKY chip.