Some coins are sleepers. Some are in a coma.

The 1879-S Morgan, Reverse of 1878 dollar is such a coin. Sometimes known by two other names, “2nd Reverse” and “Parallel Arrow Feathers,” it is a variety that many hobbyists tend to dismiss.

Those collectors are content to assemble a date set with the much more common 1879-S Morgan, Reverse of 1879 dollar, also known as “3rd Reverse” and “Slanted Arrow Feathers.”

With so many names to identify the types, you can see why the 1879-S Morgan, Reverse of 1878 dollar is a distinct and highly collectible issue. It is required for a complete set of Morgan dollars, much like the three reverses of the 1878 Morgan dollar (8, 7/8 and 7 tail feathers).

There are more distinctions between the two 1879-S Morgan coins, beginning with the mintage. Q. David Bowers, in his Silver Dollars and Trade Dollars of the United States, notes that only 1 percent of the 9,110,000 mintage that year bore the Reverse of 1878 design. That means about 91,000 such coins were dispersed by the San Francisco Mint.

The two reverses are as much a statement about 19th century transportation as numismatics. In 1878, the first year of the Morgan dollar, the Mint went through several design variations of the reverse before selecting the one that would appear on coins throughout the rest of the series. That reverse first appears on the 1878 Morgan, Reverse of 1879 dollar, minted from June 28 of that year through Dec. 31.

Unlike the 1879-S Morgan, Reverse of 1878 dollar, the Philadelphia Mint, Reverse of 1879 coin is common, with a mintage of about 2 million. Its reverse features that “Slanting Arrow Feather” design that also appears on the common 1879-S dollar.

By 1879, the Philadelphia Mint was producing Slanted Arrow Reverse dollars while the San Francisco Mint was still using 1878 dies with the parallel arrow. Shortly after minting began with the older dies, the new reverse ones arrived at the San Francisco Mint. That’s why the 1879-S Morgan, Reverse of 1878 dollar has a much lower mintage.

Arrows are not the only distinctions between coins produced at the San Francisco Mint that year. The Reverse of 1878 features a flat-breasted eagle and smaller “S” Mint mark than the 1879 reverse, whose eagle has a rounded breast.

Thus, the 1879-S Morgan, Reverse of 1878 dollar has distinctive features that make it one of the most intriguing Morgan dollars.

Just imagine this: If it were a stand-alone issue, and not a subtype, it would be one of the most coveted such dollars, with a mintage lower than the 110,000-coin mintage of the pricier 1894 Morgan dollar.

Michael Bugeja, a coin collector since childhood, is a professor at Iowa State University and also a member of the Citizens Coinage Advisory Committee. He is a nationally known author, journalist and educator.