Tati, you have specified your coin as having a minting error. Your description tells us that the 'D' in 'DEO' is missing the bottom.
When a tiny part of a coin's design is very weak or missing, it is almost always due to a 'struck through grease' error. When coins are minted, the images for both sides are imprinted on two dies, and these dies can sometimes have leftover droplets of greasing in the nooks and crannies of the design, such as in the tiny 'bowl' in the bottom of the D.
When high mechanical pressure is applied to impart the image on the blank coin, the planchet, this sometimes leftover grease prevents the die from squeezing the coin's surface into the correct shape.
Small minting errors like this do not normally cause the coin to be worth much more, especially with coins like this one that do not have a large collector following, as it is one of the most common errors. See this CoinQuest page for an example of this type of minting error.
These coins are silver. They contain 0.27 ounces of the precious metal. Using a site like Kitco Silver, we can calculate the current silver value of the coins. With silver at about $24 US dollars per troy ounce, each coin has 0.27 x $24 = $6.50 worth of silver in it, the Base Value (BV)
The catalogs report the following values for these coins.
worn: (BV) + $2
average circulated: (BV) + $10
well preserved: (BV) + $20
fully uncirculated: (BV) + $35
These approximate catalog values (explained in our 'Important Terminology page on the top left) only apply to problem-free coins without cleanings, holes, spots, gouges or the like.
These coins have been counterfeited. One known variety of counterfeits weigh only 9.65 grams instead of the true 12 grams that the coins should weigh.