... the truth is, dug coppers are going to be pretty dingy. "Environmentally scarred," they call it. Or something like that. What this means is that you handle them with care, but even if they are key coins they are severely diminished in value.
Take the 1914 cent, for example. In brilliant full red, MS-67 certified condition, graded by PCGS it is worth $50,000. This the finest example known to exist, by the way. The lowest grade listed that is worth real money to the PCGS is MS-60, certified and graded. Those draw $60. Keep in mind these are superior coins that have never seen circulation, pockets or hand oils... let alone the dirt, sun or moisture. They are as fresh as when they rolled off the press.
So what is a grubby, old 1914 cent worth, as dug from the dirt? Depends on the actual circulated condition of the coin itself.. remember it was in circulation if it was lost. Now, subtract the damage from environmental scarring. Then factor in the fact that it was dug - a no-no to collectors.
What're you left with... $1? $2? If you're lucky.
You can spank them up with electrolysis, and you may wish to treat such coins to that process. Also, toss in a measure of respect, as you do. Good for you.
But, even dug key date cents, once cleaned with electrolysis, are going to show their condition under close scrutiny. Keep your expectations low on those old coppers and you'll do alright.
Now, where there is a 1914 cent there might be a 1916-D dime, and those fare far better in the ground.... and are worth an awful lot more. So keep looking.