Yeah, I don't know the war history and "ghoulish" is just all about the perspective.
Mostly, I'm thinking of it in these terms so that I realize I don't have any feeling of attachment to it. I loved my grandfather, and I have a lot of his old tools and THOSE really mean something to me. I'd never sell them. I think of him every time I use them. But this thing doesn't connect me to him at all. It's more about my great grandfather, and he didn't even fight in the war, so it's just some thing he collected after the fact. And since nobody alive today ever met him, I have no feelings for him. He sounds like a bit of a jerk though, if he didn't like my grandfather simply for having German parents.
Here are some pictures. The remaining leather liner is very brittle, so I didn't turn the helmet right side up for any of these, because the remaining liner would probably break off and fall out.
Here's the inside.
And this is a detail that shows the metal liner band, meaning it's at least a M17 date wise. And the chin strap hardware looks like hardware that I've only seen in pictures of German helmets. There should be a maker's stamp here, but I can't see one. Either it's really faint, or it's non-existent. If it's non-existant, I think that means it's an Austro-Hungarian helmet, but they have different chin strap hardware in every picture I've seen, so I think it's German.
This detail shot shows "66" stamped in the liner head band. That's the size in cm, and is a little on the large side, but was fairly common.
And here's a side shot. That "frankenstein" lug on the side only appeared on WWI helmets, so this is definitely a WWI M17 or later helmet. Probably German.
This one, on eBay, is almost identical. It just sold for $232 here in the US market. It has no trace of liner, and mine has a little bit of leather liner left. But mine is missing one liner pin, and the visor has a slight bend to it.