A fundamentally rare coin is one that had a very limited mintage. All regularly issued business strike and proof coins with mintages under 10,000 pieces are fundamentally rare in any condition obtainable. This category includes all early gold and silver coinage as well as some copper and nickel pieces. For example all of the quarter eagles of 1796 to 1807 are in this category.

The largest mintage was in 1807 with 6,812 pieces. Both PCGS and NGC have certified 254 pieces in all grades, and these numbers do not account for crossovers or resubmissions. Obviously no more than 254 collectors could have one of these certified coins, making them always in demand. Yet mintages of other years are significantly lower. The next highest, 1804, is less than half at 3,327. Both services have 147 combined including both 13-Star and 14-Star reverses. All early date quarter eagles are fundamentally rare and would make an excellent choice for a box of twenty.

A conditionally rare coin is one that has a large mintage but saw much circulation and is common in circulated grades but rare in uncirculated or almost uncirculated condition. An example is the 1861 half eagle. It had a mintage of 688,084, making it a fairly common date. In circulated grades it retails for less than $600. Yet in Mint State 65 it lists for $37,050 and in MS66 a whopping $71,500. Clearly upper mint state grades of this coin are desirable because they are conditionally rare. NGC has certified 1456 in total but only 8 in MS65 and 2 in MS66. PCGS has 715 in total with 7 in MS65 and 1 in MS66. While these examples are sufficient to make the point, there are numerous other examples one could choose.

Some coins appreciate slowly in value and others jump up quickly. For example, the 1860-O silver dollar increased from $5,560 to $6,940 since July 2005; however, if we look at the 1860-O in MS65, we see an increase from $16,880 to $35,930 in that same period of time.

The foregoing are isolated examples of the kinds of changes in value that quality selected coins can undergo over time, and these examples are taken only over the past five years. A box of twenty well chosen pieces held over time will yield some spectacular results, and the time to begin with your twenty might never be better than it is now.