You have an interesting engine!
If you remove the steam chest cover you will be able to figure out the porting.
Regarding a gear driven cam or eccentric shaft, the design is an older one.
The New England Wireless and Steam Museum has a Herreshoff Triple Expansion Marine steam engine built 1904. These were originally designed and built as torpedo boat engines in the late 1800's.
Here:
The New England Wireless and Steam Museum is an electrical and mechanical engineering museum emphasizing the beginnings of radio and steam power.
Gil