The u64 pin is spelled the way the program that motivated it is

test/test_flan.ml

@@ -1002,12 +1002,12 @@ let () =
   (* The literal rule is untouched, which is what keeps a u64 constant's
      arithmetic at u64 rather than defaulting the 1 to an i32. *)
   accepts "a literal still takes the other operand's type"
-    "(defconst fnv u64 14695981039346656037) (defn f [] u64 (+ fnv 1))";
+    "(defconst fnv u64 0xcbf29ce484222325) (defn f [] u64 (+ fnv 1))";
   (* The form DISCUSS.org's note named: an unannotated let of a u64 constant.
      It binds a u64 and nothing about widening reaches it — a let with no type
      has no expectation to widen against, and the constant is what it says. *)
   accepts "an unannotated let of a u64 constant still binds a u64"
-    "(defconst fnv u64 14695981039346656037) \
+    "(defconst fnv u64 0xcbf29ce484222325) \
      (defn f [] u64 (let [h fnv] (* h 2)))";
   (* Shifts are the carve-out: the value's type decides and the count widens
      to it, never the reverse, because the result's width and the poison check