With the Iron Cross, a skull, and a German helmet I'd say it's a German military fantasy item. The German helmets with the spike (picklehaube, auf Deutsch) were used in WW1 and before and were made of leather with a visor at either end. Like this one...
Your helmet is the shape of the steel helmets (stahlhelm) which first came out in 1916 during WW1, but they had lugs on the sides like this one...
By WW2 the lugs were gone and I guess yours looks most like a WW2 helmet. Here's a Waffen-SS helmet from WW2...
The Iron Cross was issued during wartime only. 1813, 1870, 1914, 1939, and 1957, and was issued for bravery.
The Germans used the skull or "death head" (totenkopf) a lot in WW1. Just a little something to intimidate the enemy. "Mess with us and you'll end up like this skull". Here's a veteran pin with a totenkopf and iron cross.
The skull and bones in WW2 are mainly associated with the SS. They wore a skull and bones emblem on their hats. The skull and bones emblem, the SS runes and the swastika are all regarded to this day as offensive symbols in parts of Europe and elsewhere. Here's an SS hat pin. Gary