What were the remarks for the coach having a class from 1928 of Cid-21B?
CREATE TABLE "iron_coaches" (
  "class_to_1928" text,
  "class_from_1928" text,
  "seats" text,
  "quantity" real,
  "year_s_of_manufacture" text,
  "remarks" text
);
SELECT "remarks" FROM "iron_coaches" WHERE "class_from_1928"='cid-21b';