Saleable Products, Los Angeles CA, design patent 1945.
(5.75" x 5.75" x 1.25" cardboard box with 5.5" x 5.25" x 1.25" puzzle)

Shown on plate XII, and pages 172-173, 228 of Hordern's book, which presents this solution:

Notation: A1&A2 = left train, B1&B2 = right train, L, R, S = left, right, side tracks
A1 goes to R, A1 backs into S (pushing the freight cars to make room)
B1 & B2 go to L and attach to A2
A1 goes to R
B1 & B2 pull A2 to R, B1 & B2 push A2 into S, B1 & B2 detach from A2 and go to L
A1 backs into S and attaches to A2, A1 & A2 go into R

Further Reading
Sewell Design Patent, from: www.uspto.gov - patent no. D140,371