The Lionel 1043-500 Transformer came with the Girl’s Set that was available in 1957 and 1958. It would control one train. It does not have a built-in circuit breaker, but after 1957 Lionel would offer the No. 91 Circuit Breaker that could be used with this transformer. This is the C Variation of the No. 1043 and has an additional 10 Watt capacity even though Lionel would not change this figure on the box. Also see: No. 1043.