Nothing, same method of production. No computers, no modern machines. No ISO 9001, Mehmet is still alive.Just one question: which exactly Istanbuls you've owned/ played?Small correction, Agop and Mehmet discontinued customisation possibility. Bosphorus still does.
This thread started, about a specific cymbal that someone really liked and it became about finding another that was similar.
All of the hand made cymbal brands mentioned here could conceivably be similar, due to variables in the blank(alloy,impurities,rate of cooling),the milling,firing, tempering,hammering,bell conformation,lathing or not AND the stick being used for the soundfile.
Two Ks with very similar weights, can sound remarkably different and so can these more modern cymbals , without them being regarded as necessarily inferior.
I import custom weight cymbals from a small Turkish factory that pours their own blanks and I can tell you that some of them , you would swear are old school K's, and some of them you would swear aren't, because they are still being made with similar variabilities(albeit a little more controlled,perhaps) that the old K's were created under.
Isn't that what makes all of the above mentioned cymbal makers great? That you are offered the priveledge of discovering their uniqeness, that they haven't completely gone over( some more than others) to the mass market mantra of consistency as their one and only guiding principle?