Joe,
The "Speed Lettering" first appeared on the HTv class that were built in 1955, numbered 86000-86699. The next group of HTv's that were built in 1957 87000-87999 were also built new with Speed Lettering.
Previous orders for AAR Standard offset twin hopper cars in the HTv class were painted new in the 9" Roman Style lettering scheme. These were HTt 81000-81999 built in 1948, HTu 82000-82749 builtin 1949, HTv 83000-83999 built in 1950, HTv 84000-84999 built in 1951, HTv 85000-85999 built in 1952.
Cars within the 85000-85499 series were dedicated to stone service and identified by an orange panel with black lettering on the extreme left panel of the car body.