Congratulations on an excellent find. If that one don't make you do a happy dance, nothing will! My advice would be to not clean it. Rinse it and let it air dry, if anything. Then take it to a coin shop to have it sent in to be slabbed and graded.
I sent the one I found with the X-TERRA last November to PCGS, and they would not assign a grade, due to it being a dug coin. That patina that many of us find so attractive is considered "environmental corrosion" to the coin grading services. For $75.00, they certified it as Genuine and slabbed it. The second one I found this past July with my E-TRAC was sent to NGC and it isn't back yet. According to the coin shop who sent it in for me, NGC would provide a "details" grade, so it would be a generic "VF details" rather than the standard "VF35" etc. It would be a step above PCGS's "Genuine" designation. He also told me that there are some grading services who might assign a letter and number. But suggested that they were not as highly regarded to collectors. And a person is better off having PCGS or NGC slab it, and let a potential buyer determine the grade (and value, if you ever decide to sell it).
It may be more rare than previously believed........Mint records indicate that there should have been 852,500 of these minted. the typical die can strike about 200,000 coins. For a mintage of 4 times that amount we should see many more obverse and reverse dies. For circulations strikes, the Mint Report for 1878 states that 3 obverse dies and 6 reverse dies were made in 1877, but only 2 obverse dies and 1 reverse die were actually used. The remaining reverse dies were used in 1878. This is important, as one must ask where are the other coins? If they were struck with 1877 dates, we should find at least one example from a different reverse die. If the Mint Report is correct, and there is no reason to doubt it, then there is one obverse die used that we have not yet seen. It would be expected that if a new die was made for the 1877 issue it would have been a Bold N die. Since all 1877 Indian Cents except for Proofs are struck from a pre-1870 Shallow N die, it seems that there is a huge amount of coins missing.
And this........The 1877 Indian Head Cent is known as a key date coin of the series. There were 852,500 pieces reportedly produced for circulation, although Rick Snow* suggests that only 200,000 coins were struck. Whatever the number is, the coin is rare in all grades.
*ANA awards Rick Snow "Numismatist of the Year" 2010
Again, congratulations on an excellent find. HH Randy