When was the motor gear of the LMS 1946 no. 1901 model fitted?
CREATE TABLE "details" (
  "lms_1932_3_no" real,
  "lms_1946_no" real,
  "br_no" real,
  "date_built" text,
  "date_motor_gear_fitted" text,
  "withdrawn" text
);
SELECT "date_motor_gear_fitted" FROM "details" WHERE "lms_1946_no"=1901;