The model 25's were made continuously from 1913 to 1978. Yours was made after 1936 and has a longer cocking lever than the earlier guns. They were made with both straight stocks and pistol grip stocks like yours. In 1950 they switched to painted metal instead of blued metal in an effort to cut costs and the plastic stocks followed soon after.
Thats a very nice rifle you have, a great find and a great job of preserving it by the previous owner.