Which class to 1928 value had years of manufacture of 1921/23 and class from 1928 of BCi-21?
CREATE TABLE "iron_coaches" (
  "class_to_1928" text,
  "class_from_1928" text,
  "seats" text,
  "quantity" real,
  "year_s_of_manufacture" text,
  "remarks" text
);
SELECT "class_to_1928" FROM "iron_coaches" WHERE "year_s_of_manufacture"='1921/23' AND "class_from_1928"='bci-21';