@@ -2445,6 +2445,10 @@ mod _datetime {
 
     // timezone
 
+    /// timezone(offset, name=<unrepresentable>)
+    /// --
+    ///
+    /// Fixed offset from UTC implementation of tzinfo.
     #[pyattr]
     #[pyclass(module = "datetime", name = "timezone", base = PyTzInfo, traverse)]
     #[derive(Debug)]
 
@@ -3303,6 +3303,10 @@ impl Py<PyType> {
         Ok(())
     }
 
+    /// __prepare__($cls, name, bases, /, **kwds)
+    /// --
+    ///
+    /// Create the namespace for the class statement
     #[pyclassmethod]
     fn __prepare__(_cls: PyTypeRef, _args: PrepareArgs, vm: &VirtualMachine) -> PyDictRef {
         vm.ctx.new_dict()
 
@@ -441,7 +441,43 @@ const fn write_signature_prefix(buf: &mut [u8], name: &str, args: &[SigArg]) ->
     put_str(buf, st.n, ")\n--\n\n")
 }
 
+// Explicit Clinic headers cover legacy signatures that are not Python parameter
+// lists. Recognize only a complete header, not a call example in prose.
+const fn has_internal_doc_signature(name: &str, doc: &str) -> bool {
+    let name = name.as_bytes();
+    let doc = doc.as_bytes();
+    if doc.len() <= name.len() || doc[name.len()] != b'(' {
+        return false;
+    }
+    let mut i = 0;
+    while i < name.len() {
+        if doc[i] != name[i] {
+            return false;
+        }
+        i += 1;
+    }
+    while i + 5 < doc.len() {
+        if doc[i] == b')'
+            && doc[i + 1] == b'\n'
+            && doc[i + 2] == b'-'
+            && doc[i + 3] == b'-'
+            && doc[i + 4] == b'\n'
+            && doc[i + 5] == b'\n'
+        {
+            return true;
+        }
+        if doc[i] == b'\n' && doc[i + 1] == b'\n' {
+            return false;
+        }
+        i += 1;
+    }
+    false
+}
+
 const fn write_internal_doc(buf: &mut [u8], name: &str, args: &[SigArg], doc: &str) -> usize {
+    if has_internal_doc_signature(name, doc) {
+        return put_str(buf, 0, doc);
+    }
     let n = write_signature_prefix(buf, name, args);
     put_str(buf, n, doc)
 }
@@ -930,6 +966,40 @@ mod tests {
         assert_eq!(rendered(DefaultRepr::Unrepresentable), "<unrepresentable>");
     }
 
+    #[test]
+    fn explicit_internal_doc_preserves_legacy_signatures() {
+        const DOC: &str = "index($self, value, [start, [stop]])\n--\n\nFind a value.";
+        const ARGS: &[SigArg] = &[SigArg::from_arg::<crate::PyObjectRef>("value")];
+        const N: usize = super::internal_doc_len("index", ARGS, DOC);
+        const TEXT: [u8; N] = super::internal_doc_bytes::<N>("index", ARGS, DOC);
+        assert_eq!(&TEXT, DOC.as_bytes());
+        assert_eq!(native_call_flags(ARGS, false), PyMethodFlags::O);
+        assert!(super::has_internal_doc_signature("f", "f()\n--\n\n"));
+        assert!(super::has_internal_doc_signature(
+            "f",
+            "f($self, value='é',\n  other=None)\n--\n\nBody."
+        ));
+    }
+
+    #[test]
+    fn prose_and_incomplete_headers_keep_generated_signatures() {
+        for doc in [
+            "f()",
+            "f()\n--\n",
+            "f()\n\nExample.\n--\n\nBody.",
+            "f(first,\n\nsecond)\n--\n\nBody.",
+            "g()\n--\n\nBody.",
+            "ff()\n--\n\nBody.",
+            " f()\n--\n\nBody.",
+            "Example: f()\n--\n\nBody.",
+        ] {
+            assert!(!super::has_internal_doc_signature("f", doc), "{doc:?}");
+            let mut buf = vec![0; super::internal_doc_len("f", &[], doc)];
+            super::write_internal_doc(&mut buf, "f", &[], doc);
+            assert_eq!(buf, format!("f()\n--\n\n{doc}").as_bytes());
+        }
+    }
+
     #[test]
     fn native_call_flags_from_params() {
         const fn arg(params: Option<&'static [Param]>) -> SigArg {
 
@@ -45,6 +45,10 @@ mod _collections {
         n: isize,
     }
 
+    /// deque([iterable[, maxlen]])
+    /// --
+    ///
+    /// A list-like sequence optimized for data accesses near its endpoints.
     #[pyattr]
     #[pyclass(
         module = "collections",
@@ -599,6 +603,12 @@ mod _collections {
             self._extend(&iterable, true, vm)
         }
 
+        /// index($self, value, [start, [stop]])
+        /// --
+        ///
+        /// Return first index of value.
+        ///
+        /// Raises ValueError if the value is not present.
         #[pymethod]
         fn index(
             &self,
 
@@ -362,3 +362,52 @@ class NewList(list):
 else:
     assert _hashlib.HASHXOF.update.__text_signature__ == "($self, obj, /)"
     assert str(inspect.signature(_hashlib.HASHXOF.update)) == "(self, obj, /)"
+
+# Legacy Clinic headers are useful raw metadata even when their optional groups
+# or sentinel defaults cannot be represented by inspect.Signature.
+import collections
+import datetime
+
+for obj, raw, doc in (
+    (
+        collections.deque,
+        "([iterable[, maxlen]])",
+        "A list-like sequence optimized for data accesses near its endpoints.",
+    ),
+    (
+        collections.deque.index,
+        "($self, value, [start, [stop]])",
+        "Return first index of value.\n\n"
+        "Raises ValueError if the value is not present.",
+    ),
+    (
+        collections.deque().index,
+        "($self, value, [start, [stop]])",
+        "Return first index of value.\n\n"
+        "Raises ValueError if the value is not present.",
+    ),
+    (
+        datetime.timezone,
+        "(offset, name=<unrepresentable>)",
+        "Fixed offset from UTC implementation of tzinfo.",
+    ),
+):
+    assert obj.__text_signature__ == raw
+    assert obj.__doc__ == doc
+    try:
+        inspect.signature(obj)
+    except ValueError:
+        pass
+    else:
+        raise AssertionError(f"legacy signature should remain unrepresentable: {obj}")
+
+# __prepare__ uses $cls, unlike the $type receiver of most native classmethods.
+# The descriptor and its bound form must expose the same header but strip the
+# bound receiver only from the latter's inspected signature.
+prepare = type.__dict__["__prepare__"]
+assert prepare.__text_signature__ == "($cls, name, bases, /, **kwds)"
+assert str(inspect.signature(prepare)) == "(cls, name, bases, /, **kwds)"
+assert type.__prepare__.__text_signature__ == prepare.__text_signature__
+assert str(inspect.signature(type.__prepare__)) == "(name, bases, /, **kwds)"
+assert type.__prepare__.__doc__ == "Create the namespace for the class statement"
+assert type.__prepare__.__self__ is type