UP storage mail car By Angela Cotey | November 10, 2017 | Last updated on August 8, 2025 Email Newsletter Get the newest photos, videos, stories, and more from Trains.com brands. Sign-up for email today! Get Updates Union Pacific No. 5702 was assigned and lettered as a mail storage car. Built by ACF in 1949, it was a long (85-foot) streamlined lightweight car riding on six-wheel trucks. Union Pacific photo