"A rather fanciful early 1940s postcard, showing what appears to be a New York BMT ""Bluebird"" train in the Chicago subway. The four experimental articulated cars 5001-5004 (later renumbered to 51-54, and not to be confused with the current 5000-series) were based on the Bluebird design and were delivered in 1947-48. (CERA Archives)"
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