Quote:
it might as well be the one you're suggesting Q6. If it's Q6, does it still have any value in this state?
Actually, I wasn't "suggesting" that your stamp is Q6. I used that as an illustration of a color that is close to the one you had said you thought it is. I'm going to guess, that you tried to compare your stamp to a color picture in a catalog (perhaps online) and chose the one to which it looked closest. Am I right?
Let me try to show you the problem. Here is a group of varieties of the 1861 24c from my collection. All were scanned together so they have the same light source.

All the stamps in the top row were sold to me as varieties of US Scott #70, and the three in the bottom row as varieties of #78. There's a lot of overlap isn't there. Do you think the sellers were right?
I started collecting stamps nearly 60 years ago, and for the past 50 of those years I have paid a lot of attention to the US classics. Yet, if I did not have a reference collection to guide me, I would not be able to sort these particular stamps correctly. For the 1861 issues, color is the principle way of determining the issue to which a particular stamp belongs.
Unfortunately, colors online vary from one monitor to another for the same pics. So how could I or anyone here possibly tell you which color stamp you have with any certainty? On my monitor your stamp does not seem to have much red in it; it looks like mostly a grayish shade. For me that puts it in the later group (my second row), US Scott #78. The three most common shades of that type range in catalog value from $350-450, so if your stamp were undamaged, without thins, tears, stains, or anything not intended, I might offer $250 for it at auction and would have a good chance of getting it depending on competition that day. But with that missing corner, you would be lucky to get 10% of that, and it is more likely that you would get less, maybe half of that. Too many undamaged copies with a less interesting cancel or not as well centered are available for anyone to offer much for a damaged stamp. If you figure your stamp at $15 or less, you will be close to the truth.