Kurt,
I believe the photo of the three cars is at magic mountain. if i zoom in one can just make out a "4" as the last # on the boxcar. it had been pontificated in the past that the roof had been rebuild at some point eliminating the roof hatches. it is my belief that car #s were swapped based on the buffer difference according to published sources other renumbering took place on one of the stock cars around this time as well.
it is my belief that the first group of boxcars #8193-8292 used this style of buffer block.
the second group # 8293-8419 used this style buffer block, along with the steel under frame stock cars built in 1910.
Al P.