The 1918-S Buffalo nickel is one of the best of a very good group that is often overlooked. At today's price of $28,500 in MS-65, it is one of the best of the branch mint Buffalo nickels from the teens and twenties. However, the 1918-S did not follow the pattern perfectly for Buffalo nickels at the time.
The Buffalo nickel's reverse had been changed the first year. The Buffalo was placed on a flat line rather than a mound, so "FIVE CENTS" was no longer on the highest part of the design and wouldn't wear off quickly.
Interestingly enough, there did not seem to be similar concern for the obverse, where the date was the highest part of the design. Perhaps it was thought that the denomination was important on a nickel, but the date was not. Regardless, the date started to wear off very quickly. Although it could be restored by etching acid, the fact remains that those coins are fillers. Finding even a G-4 of some dates is a challenge.
For example, in the G-4 Buffalo pricing dates like the line type San Francisco and Denver coins are very expensive considering their mintages. A host of other dates are also fairly expensive, but the 1918-S strangely is not. It is $14 in G-4. It had a mintage of 4,882,000. The line type 1913-D had a mintage of 4,156,000, yet it is $125 in G-4. It appears that more 1918-S coins lost the date than other years.
There was no real saving of Mint State Buffalo nickels besides a few of the first 1913 coins. What collectors there were probably collected only by date. If a 1918 was needed, the collector probably obtained the Philadelphia coin. It had a mintage of more than 32 million. The 1918-S was not a likely choice for collectors outside of San Francisco.
These factors are why the 1918-S is $495 in MS-60. While the 1918-S is not the key Buffalo nickel date in MS-60, it is far tougher and more costly than one would expect based on its mintage. In fact, it's more in MS-60 than a lot of lower-mintage dates such as the line type 1913-D, and the 1914-S and 1914-D.
At $28,500 in MS-65, it's safe to suggest that the 1918-S is in very elite company. Numismatic Guaranty Corporation has graded 258 examples of the 1918-S and just five reached MS-65 or better. Professional Coin Grading Service has graded a total of 456 and only 24 reached MS-65 or better. Just one example was called MS-66. The small numbers prove the lack of saving and the lack of quality. Branch mint Buffalo nickels of the period were often poorly struck.
The 1918-S is seemingly more available than one would expect in lower grades, tougher than one would expect in Mint State and simply rare in the highest of grades. That's a very unusual combination, but it makes the 1918-S a very interesting coin.