I think perhaps the pre-war IRT had more distinctions than that of the standard IND. Don't get me wrong, though. I loved the R-1-9 series.
But the Hi-V's had differences: window arrangements, railroad roofs vs Deck roof. MUDC vs manual doors. Yes, there was variety.
And each division seemed to have its own odors. Always associate juicy fruit gum with the old IRT. Dnetyne with the new R17's.
The R22 came in with sealedbeam headlights; all prior cars had plain headlights. The view from the front of a car without bright headlights and with bulbs on the interior gave a neat effect; you almost felt part of the train, especially if the front window dropped down, like the BMT had.
srandards.