Probably a Stubai model. They made three or four different weights and head shapes. Yours is the mid-sized version or the model they called the "descending hammer" (hard to tell from the picture). Similar head designs and weights have been around for a long time. The first civilian hammers of that type were produced in the early 50s and remained unchanged into the 70s. From the handle and what I can see of the tangs I would guess mid 60s vintage. The older handles were a bit fatter on the ends and had a nice narrowed section in the middle (like yours). Without really holding it and studying the details it's a tough call to date it any closer.
I hope this helps. Nice hammer.
Brian in SLC is right. Look very closely for markings on the front tang just under the head. They are often faint and tended to get obliterated by missed piton strikes.