Bill Vaughn wrote:

3.Regardless of what the rule said it would have been up to the crew to secure if they desired. All cabooses and passenger cars used the same key on every railroad as far as I know.

Not true on the SP in the days when cabooses were assigned to individual conductors. The conductor had the only key to his assigned caboose, except for the Master Mechanic's office. Maybe later in the pool-caboose days, they used universal keys.
I agree with Dennis Storzek: the bars inside the window were to prevent crewmen from breaking the window if they fell against it. Anyone who has never experienced slack action in a caboose has no IDEA how violent and abrupt this can be.

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