The United States Mail No. 3428 was produced in 1959 and 1960, with Type IIB and Type III bodies. The car has a plunger mechanism that would open the door and the mail carrier would "pop out" holding a mail bag with the use of a UCS or No. 6019 track uncoupling section. Came with early AAR trucks with disc couplers.

This operating car has three variations:

Variation A: Type IIB body, GRAY man with a GRAY mail bag
Variation B: Type IIB body, BLUE man with a BLUE bag
Variation C: Type III body, BLUE man with GRAY bag