First air rifle with a 2 stage trigger?

[ccdjg]

Anyone have an idea when the first 2 stage trigger appeared on an air rifle, in particular a springer?
The handfull of pre war springers I've shot are adjustable for weight but single stage.

Also maybe the early resevior rifles or CO2 rifles?

Cheers,
Matt.

Are you excluding double set triggers from your definition of a 2-stage trigger, as these date back more then 200 years for long barrel airguns?