SRS 403, an all-ultrasonic car, is ex New York, New Haven & Hartford Railroad 18. It was one of ten model FCD railbuses built by the Mack Company for the NYNH&H.

The first car, #10, was completed in October 1951. This initial car operated very successfully resulting in nine more being ordered by the NYNH&H, road numbers 11-19 inc. These were delivered in July and August of 1954. However, Frederick C. Dumaine had been succeeded by Patrick McGinnis as president of the New Haven by the time they arrived. McGinnis disliked the FCDs and immediately placed them in storage. None ever operated in revenue service except for #12 which was used for approximately two and one-half years. It then joined the other cars in storage. Later, Sperry Rail Service purchased two cars and two were sold to the Remington Arms Company in Bridgeport, CT. The remaining six were sold to Spain, however, these were lost at sea when the boat carrying them sank some 400 miles out of Boston.

In July 1985, Sperry acquired Remington Arms 2, originally NYNH&H 15. Sperry used the car as a parts source only and it likely was never assigned an SRS fleet number.

For more information on former NYNH&H 15, visit the following sites:
Danbury Railway Museum gets boost and Historic FCD Railbus now at DRM.

Other reference material on the Mack FCD can be found in Extra 2200 South February-March 1969 page 16.