Heavier weights -- could also be 15" rock hats, but then again, it was the 70s and most stuff was heavy.
Zildjian 15" Hollow Logo Avedis Hi Hat Cymbals (Late 1970s) Pair
1970s Zildjian A 14" New Beat Hollow Logo Bottom Hi Hat Cymbal 1460g
Hi-Hat Cymbals 14" Zildjian Avedis New Beat 1970s USED! RKZHZ220326
Zildjian Avedis 15" New Beat Hi Hat - Bottom Cymbal ONLY - 645g
Zildjian Avedis 15" New Beat Hi Hat - Bottom Cymbal ONLY - 1616g
Zildjian 15" Avedis New Beat Hi-Hats