Sometime due to ground corrosion, it is hard to get the coin in better condition.
I have had the same results as you on some coins.
Most of the time they come out clean after a very short time which is why I said to take it out after about 2 minutes and check it.
The peroxide will not harm the coin, but sometimes after taking the corrosion off of a coin with this method, it actually looks worse due to the coating making the coin look better. After removing this coating you can see rough surfaces and loss of detail.
If it has not changed at this point, that is probably the best it is going to get in my opinion.
I have some that I wish turned out like yours.. they are in really corroded to the point I can't even get a date of of them.
As you find others down the road, try the peroxide on them.. I think you will be amazed at the results on the right coin.
If you open up my post below, you will see an 1852 large cent I found today. When I first found it, you could not make out anything at all on the front and very little on the back.
I knew it was a large cent by the size when I found it.
I got home and put in some peroxide and it the results are after just one dip for about 2 minutes or less.
Now the coins is badly corroded and pitted,but this is not due to the peroxide.
It is the ground eating at the copper over the years and no method is going to fix this.
Heck, I'm just glad to be able to get the date off of this one after seeing its condition out of the ground.
That coin is not in bad shape and a good find.. congradulations!!!!