
areas in question are inside of the numbers/mint marks are often a pin that creates the center of the device. When these break off, then that area is not formed, but left filled on that area. On the 1960, there was an issue with the small date dies because of die chipping, the recreated a die call the large date dies. On the Denver dies, there were about 50/50 percent on the large and small date dies. On the Philly cents there were more large date dies used that year. So the Philly ones do carry more of a premium especially on the BU examples. Same on the Proof cents. The small dates are more rare than the large date proofs. So on your coin the 1960-D small date is common. The issue on your coin was a die chip forming on the inside loop of the 6. While this area is not a pin like on the 1958
Wheat cent, the die chip broke off the die and now is leaving an unshaped void where it is missing.