Old Western Pacific wooden steam era caboose in modern 1950's era orange and silver paint. From the internet.

Wooden railroad cabooses are one piece of rolling stock that one definately associates with being from the steam era.

Some railroads like the Western Pacific, The Chicago, Rock Island & Pacific and the Burlington Northern actually utilized them long after their service lives would have been over. They were eventually outlawed from mainline train operations because of safety issues when steel cabooses began taking hold as the industry standard.

The Western Pacific and the other railroads I mentioned, used their remaining wooden caboses on transfer trains and switching locals. The Burlington Northern and The Chicago Rock Island & Pacific did so well in to the late 1970's, and some have been preserved.

This Western Pacific example with the blanked out cupola windows, appears to have just came out of the railroad car shop, as the car is shimmering in a very shiny coat of fresh WP orange and silver 1950's era California Zephyr colors.
The blanked out upper cupola windows indicate that this caboose has already been downgraded to transfer train and switching local service.