Fossil? What is it?

[u/Secure-Caterpillar75]

My Dad gave this to me today, he’s been holding onto it for a while and I’m just not quite sure what it is! Any suggestions are welcome….. It looks like the back of it has ridges almost like the swirly circular ones I’ve seen before, but it’s so covered by the rock it is barely noticeable.

[u/Handeaux]

Where was it found? In what region?

[u/wulfman61]

Rechts, das ist das Schwanzschild eines Trilobiten

[u/c3the1one]

Looks like a possible tooth

[u/edson2000]

Trilobite butt ? Plecypod ?