Cephalopod fossil?

[Moose Man]

Relevant info first: This was found in Petoskey Michigan while looking for Petoskey stones. It was found in partially buried in sand. It is quite large and rather heavy. As pictured in picture 5, there is some sort of opening at the end? I can't get a very good picture of the inside, it's hard to get light where i need it and take a picture. the hole looks to maybe be about a 1/2 mm deep, and less than that wide. I took to reddit, albeit with less detailed photos and was told it was a straight shelled nautiloid cephalopod from the paleozoic, and that it was a brevicone, which I'm hoping someone can confirm or deny, or point me towards relevant info. I was trying to find more and found this on your forum, which is the first thing I've found online that actually looks something close to what I have: 

 

 

Anyways, Thanks for looking, and any help you can offer.

[Thomas.Dodson]

A paleozoic brevicone nautiloid is correct. Petoskey stones come from the Devonian Traverse Group in the Gravel Point Formation so this is likely Devonian although I don't know the extent of other formations in the area.

 

Note that the portion you've primarily photographed is the phragmocone but it looks the constriction and part of the body chamber might also be present.

Something like Acleistoceras sp. maybe. I don't have much experience with paleozoic cephalopods and siphuncular sections are often needed to ID but in this case there's a report detailing species of the eastern Michigan rough stratigraphic equivalent of the Gravel Point Formation, the Alpena Limestone. LINK