That's a later on K.... 60's.

It's hard to say if it's a hihat, but...

the k's never had stuff like "top", "bottom" or "ride" printed on them like A's did.

They basically made cymbals and it was up to the drummer to decide what it was. I always got the feeling that after the basic shape was pressed that when they trimmed off the edges they made it as big as they could - that's why my old K's are odd sizes like 17 1/2" etc... it seems like it would be sheer luck if they ended up on the number, like a 13" or 18" 'cause it doesn't seem like they cared much about that.

Most people will tell you to listen to it, and decide from there, and not care about much else.

My guess is that it was a hihat, because I've never heard of anyone buying a 15" cymbal for anything else.

I have only one of the K's in that era, a 20" that I bought new decades ago, and every few years I get it out in hopes that I will like it but it hasn't happened yet. It's only stellar with mallets in recordings.

My gut feeling is that $150 is a bit high, maybe not.

If it has the K sound, a 15" crash would be very useful; I use a 15" A hihat for a crash (it has a huge cutout) and it sounds very good.