That is a K Dark Crash from 1987-early 90’s. The K Custom Dark Crash was introduced in the mid 90’s.

First, it's a K Dark, not a K Custom Dark and is similar to one that I had but sold a year ago. I say similar to mine in that the hammering on this one isn't as pronounced. It's a pre-serial number K, so I would guess late 80's - early 90's. Interestingly, the "Dark Crash" stamp is inverted from the stamps you usually see identifying the cymbal type and size.

That was normal for the non "A." Zildjian lines at the time.