Didn't get a reaction of the museum but did a internet search on the patents of this car. Couldn't find any related patents registrated on the dates wich are shown on the side of the car but a serach on Ralston and ore care gave me this result wich I found interesting and usefull: https://www.google.com/patents/US1124188
There are some drawing in it and when you download the pdf file (perhaps you need a google account for it) also the original text is visible.
One of the drawings:
Its a bit a technical drawing but the number 9 is a rod wich presses against the doors through rollers 10. I think they're also visible on the photo posted earlier:
When the racked rod, number 30, was replaced by a wormwheel then maybe there was no need for a locking system, however I think there was one.