The stretcher is what the canvas is stretched over and is made of wood. The cast iron device dated 1885 was an attempt at improving the traditional wooden keyed stretcher by Aaron Draper Shattuck (ADS). It was used for a short time but was abandoned I think because it didn't allow for natural shrinkage of the wood. Earlier canvas supports (1860 back) were flat-cut butt joints with no miters and called strainers and allowed no consistent adjustment. Wooden "keys" along with the mitre cut stretchers allowed a safe adjustment and are still in use today.
Your painting is an amateur landscape that should just be enjoyed for what it is, an amateur 1880's potboiler with a minimum value.
