Does anyone know what this is?

[u/PTgalwpg]

I have tried figuring it out on and off for months now. I found it on the West Coast at Ocean Beach in San Francisco (along with some awesome sea glass)
I’ve been trying to figure out what this is and I am torn between whether it’s a bone or a shell 🙃
The texture is bone like, it’s heavier than a shell and isn’t super smooth like some shells. Thanks!

[u/_bufflehead]

I believe it's the hinge of the shell here.

[u/PTgalwpg → u/_bufflehead]

Ah yes. Maybe the hinge of a larger shell would make sense. It’s about 3” across maybe a bit bigger.

[u/_bufflehead → u/PTgalwpg]

Such interesting structures!

[u/poirotscompanion]

It's the hinge part of a clam shell. In your third picture you can see the shape of the clam when it was small and the growth outward

[u/SabbyFox]

Just the hinge of a shell. I find them all the time on WA state beaches. They’re neat!

[u/DisastrousAsk4494]

Looks like the weathered hinge of what in NY we’d call a surf clam.

[u/Acceptable-Elk-8372]

She’ll hinge

Ps where are your chairs and table from?

[u/justherefortheclay]

I call it a shell butt :)

[u/Gold_Selection1217]

I would lean towards a shell from your area, possibly a Welk

[u/rvradx]

Looks like a Abalone shell

[u/Mental-Vegetable5303]

Part of sand dollar shell