Three door baggage car

Hi I wonder if anyone can help

The Pittsburg, Shawmut and Northern had a three door baggage car. the bottom of the center door was about 18 inches above the floor and was narrow - maybe 3 feet. The doors at either end of the side were typical baggage doors with the bottom at floor level.

My question is: What would be the purpose of having a door 18 inches higher than the floor. Was there a “platform” inside - maybe for mail bags. I cant see wanting to put something into a door that was higher.

Any thoughts are help appreciated

Mark

I know that some Baggage/RPO cars had “arms” that could be used to grab a bag of mail from a pole standing off to the side of the tracks, IIRC this would be from stations that weren’t part of the listed stops for a particular train OR were enroute between the two cities of a mail-express train. No need to cut a hole all the way to the floor in that instance, it just needs to be big enough to allow a bag of mail to pass through…