As can be seen in this comparison, the earlier 72 coach on the right has smaller windows. No facts discovered as to why IVES changed this lithography, and it remains a mystery. This is often referred to as the four boards or two boards between windows.
The change to wider windows in the 72 coach is probably 1907 or 08 till 1909. The 70 and 71 cars remain the same. The change to green roofs is probably 1908 and 1909.