At 11:20 AM 4/13/2011 -0400, you wrote:
Roughly when were the H10 hoppers built?1956 (single prototype), production 1957 thru the unmentionable next zero-year.
Total cars built = 8000. Less than I thought, but still a sizeable hunk of the fleet.
N&W was still mostly a steam railroad at the time, so they qualify as steam era cars by any criteria, even though many were still in service by the time the space shuttle was flying.