These are absolutely wonderful 15" hi-hats. The top cymbal is K Istanbul old stamp IIa, so made between 1945-1949. It's Paper Thin and weighs a paltry 702g. The bottom is a Zilco 'by Azco' from Canada. It's 1200g and has a crisp clear tone. Zilco's were Canadian made Zildjians and were unlathed. I'm having a tough time dating it but it's likely made in the 1970's, however it could possibly be earlier.
The combination of the K Istanbul top and the much heavier Zilco bottom seems to work like magic. Please listen to the youtube sound files. They are perfect for Jazz. You can see in the pictures the Istanbul top is slightly smaller (by a very tiny fraction) than the standard 15" shown on the Zilco bottom.
Check out the youtube sound file (please use headphones). No EQ or Comp is used.
