1916 D Mercury Dime Verification Help

Hello all,
Is there a good place on the web that has the different things to look for on a genuine 1916 D?

Yesterday, at a local coin collectors house, I was going through some silver dimes that were at 70 cents a piece... I needed just a couple roosevelts to complete another set.

There were some mercs in there. and came across one that was a 191?. Could not really make out the last numbers, either a 6 or an 8.
Flipped it over and it had a D. So I handed it to the guy and asked him what date he thought it was. He got out his eyepiece, and after about two minutes he believed it to be a 1916, but could be a 1918.
He flipped the coin over and "Oh my god". He believes it to be a 16-D.

He asked are you going to buy that one as well. I told him well depends on if it is a 16-D and the price. He said 70 cents buys it since he bought them as scrap silver and thats what he will sell them for. Since I found it, I can have it at 70 cents.

I figured even if it is not a 16-D, what am I out? Nothing much with silver being where it is.
A former grader of SEGS came over a little bit later and looked and said it is just too hard to say one way or the other. He did not have his reference books with him. He said no doubt the D is good, just unsure of the date.

So if anyone knows of a good site that has help with 16D verification, it would be greatly appreciated if you could let me know.

I plan to post pictures of the coin tonight.

Thanks!
Jordan