The plates were not actually plates, but stones. Those were usually resurfaced after use because they were expensive and hard to store. There's some solid evidence that the P150 back stone was either poorly resurfaced or was reworked to make a p350 back stone. (too early to tell which)
The images of cards were probably laid down with transfers printed from a master plate. And that was done from the original art. There are some cards in T206 that show some indication of the masters being redone at the very least between the 150 and 350 series, and probably between 350 and 350-460 as well. The easiest to see is Conroy fielding where there either are or are not lines on his hat.
There are a few cards I've looked at that show three slightly different images for the same subject within the 150 series. I haven't gotten far enough to know if it's all of them or not.
The coupon T1s may have been the same plates, and if not were probably from the same masters.
T2 and T3 all look very different from T206, and were probably made from new masters taken from the same art. I haven't studied it all that deeply though so take that as more opinion based on a very small sample size. (My own collection, 0 Type 1s 3 type 2s and 0 type 3s ....I think I need more coupons
)At the minimum one of the blue plates and the brown plate would have been different.
Steve B
Steve B