It happened just after the transition from the trans stamp to the 50s stamp. I've seen 50s Zildjians with small holes, but very few.

I believe late 40s when the transitional period started.. the holes are smaller and things changed in the early 50 s

I believe it was in 1958. That is when the stands starting going to the 8mm tilter posts meaning a bigger hole size was needed.

Does that include K. Zildjian from Turkey? I've got a matched set of 14" K. Istanbuls where the bottom cymbal won't fit on a 60's Rogers Swivo hi-hat.

The evidence from Avedis Zildjian is 1958 or so for a shift from 7/16" to 8/16" (aka half inch).

http://black.net.nz/avedis/holes.html

It looks like Italian cymbals are roughly the same but the evidence isn't as strong. UFIP may have been using a metric drill size as well so things are slightly different. I see very occasional suggestions that Paiste may have had smaller holes in the early Formula 602 days but that evidence is still in the "not enough to be convinced" camp. If anybody has Paiste evidence I would love to hear from you.

I don't have enough data on Turkish made K Zildjian cymbal mounting hole sizes to be able to pick up whether the change happened at about the same time, or a different time, or whether K Zildjian continued to produce both hole sizes into the 1960s. The picture is always made more uncertain because holes can be enlarged post factory.

What production era are yours from kdg?

Zenstat,

As far as I can tell (I'm not an expert here), it looks to be an "Old Stamp"

(either IIb or IIIb)

The hole is 3/8ths and they are very thin 14 inchers.

We can identify it for you if you post pictures of the trademarks.

Here it is. Thanks for your help!

I hope I haven't hijacked this thread.

It is a 2013 resurrect so we won't be doing to much disservice to the original post.

That looks like a Hartrick Type IIb to me. To tell a IIb from a IIIa or IIIb

I look at

MADE IN TURKEY (III same height for the IN)

MADE [SIZE="2"]IN[/SIZE] TURKEY (II has shorter [SIZE="2"]IN[/SIZE] )

and the relative size of the two ZILDJIANs. In the IIb and IIIa they are about the same height. In the IIIb the lower ZILDJIAN is taller than the upper one.

The other test is whether or not the star just touches the tip of the crescent moon on the right. In the IIb it does, in the IIIa and IIIb the star is a little smaller and slightly away from the crescent moon.