Last week I wrote about “key” coins, meaning the coin is one of the rarest (hence most expensive) coins in a set. My suggestion in that column was that one collecting option is to focus on just the key coins in a series rather than looking to collect the an series.

The example I used was the Lincoln cent series of coins, first minted in 1909 and, with some variations, still minted today. The 1909 coin struck at the San Francisco mint is the key coin in that series, commanding a price of $650 and up. I feel purchasing this coin would be a good investment.

Almost all series of coins have their key, and the following is my opinion as to what would be a wise choice to collect.

Working our way up through the different denominations, the Jefferson 5 cent coin, first struck in 1938 and minted to this day, doesn’t have any real key date coins, but its predecessor, the Buffalo 5 cent coin, does. The Buffalo 5 cent coin was minted from 1913 until 1938 and pictured an Indian head on the face and a buffalo on the reverse.

Two of my favorites in this series — coins that are mint variations rather than the intended coins — are the 1918/17 Denver minted coin and the 1937 Denver minted coin where the buffalo on the reverse only has three legs. The reason I refer to these coins as variations is that in 1918, no dies were ready at the Denver mint to strike 5 cent coins, so a leftover 1917 die was put into service by having a 7 in the date struck over with an 8. Not many coins with this overdate were struck, so this is one key to the series that will cost around $2,000 in fine condition, the lowest grade I recommend buying.

The 1937 three-legged coin is the result of heavy die polishing by a mint employee that actually polished off the leg in the die. This coin in fine condition will cost in the vicinity of $1,000. Both coins should be authenticated and graded by a third-party company, as both are highly counterfeited, especially the three-legged buffalo. Counterfeiters have ground off the leg and tried to pass coins off as genuine, but the alteration is visible under high magnification. I’ve even seen one where the counterfeiter actually ground off the wrong leg. No one ever said these people were smart.

The next denomination is the dime. The Roosevelt dime struck from 1946 and still minted today has no coin that could truly be considered a key. However the previous series, the Mercury dime minted from 1916 until 1945, has several coins that can be rightly called keys.

First is the 1916 dime struck at the Denver mint. In 1916 both the Philadelphia and Denver mints were engaged in the minting of its predecessor, the Barber dime, and both mints had already struck millions of coins. When it was decided to change the design to the Mercury dime, the Denver mint either didn’t have the time or the need to mint more coins, so its production of coins was low, hence creating a key that will cost around $2,100 in fine condition.

Next on my list are the 1942 dimes struck at the Philadelphia and Denver mint. The same situation occurred as with the 1918 5 cent coin described above. 1942 dies weren’t ready, so 1941 dies had the 2 stamped over the 1, creating 1942/1 varieties for coins from both mints. A 1942/1 dime struck in the Philadelphia mint will cost around $375 in fine condition, while a 1942/1 dime struck at Denver will cost around $350. However, this is a situation where for a little more money, a higher grade coin could be obtained.

More on my list of keys next week.

Douglas Keefe is the president of Beachcomber Coins Inc. He and his wife, Linda, operate Beachcomber Coins and Collectibles, formerly in the Shore Mall and now at 6692 Black Horse Pike in the old Wawa building just beyond the former Cardiff Circle. They have satellite offices in Brigantine and Absecon. Between them they have more than 70 years of experience in the coin and precious metals business. They are members of the American Numismatic Association, the Industry Council of Tangible Assets, the Numismatic Guarantee Corporation, the Certified Coin Exchange and the Professional Coin Grading Service.