The 1934 National Parks Issue
(read how to value your stamp below)
You have the National Park issue from the year 1934. The 8c value is somewhat common.
The perforated variety (Scotts #747) value can be found by clicking the numbers 736-751 on the menu to the left.
The imperforated variety (Scotts #763) value can be found by clicking the numbers 752-765 on the menu to the left.