Yes, there is a device to hold the toggle open on an empty magazine (see photo). If the toggle does not lock back it could be due to a missing or worn holdopen device. More likely it is a weak magazine spring that does not allow the magazine follower button to push the holdopen up far enough to activate.
P.S. Thank you for the serial number. It is fairly early as Model 1900 serial numbers run into the 20,000 range.
P.P.S. A flying cow of doom is a pretty scary concept! Pidgeon poop is one thing but flying cows...good lord!
