70's Avedis Zildjian New Beats.
I agree with the 1970s but I'm not sure how you can be 100% sure they are New Beats from the photo of the trademark stamp. :D
Based on the proportion of New Beats vs matched pairs (similar weight top and bottom) vs Rock Hats (heavier) from that decade New Beats are most likely, but the weights will reveal which model even though the model ink has gone.
Here is my brief history of New Beats:
http://black.net.nz/avedis/new-beats.html#NBtop
and info on expected prices assuming they are 14" so you can see how thankful you should be:
http://black.net.nz/avedis/avedis-prices.html#14
and how to identify a 70s stamp:
http://black.net.nz/avedis/avedis-gallery.html#70s
Enjoy your new hats.