how to identify chain type How can I identify the make and model of a chain?

I need to take a chain off and clean it.  (It's a new-to-me used bike, and I'm giving everything the once over.)  The chain doesn't have a master link, so I'm going to have to break it and add a master link.  To do this, I need to figure out what kind of chain it is so I can get the right master link.

(It might make sense to just get a new chain given relative prices, but I'd rather keep the chain I have because this is my knock-around bike and I don't want it to look new, I want it to look not worth stealing.)

Looking at the chain, it says KMC, NARROW, with a stylized Z.  The bike is a 3x7 department store bike.  The rear cogs say Shimano MF-TZ21.

Here's a picture.
Any brand link that is rated for a 7 speed chain will fit. Sram refers to there's as a Power Link, KMC calls it a Missing Link other are quick connect. What is important is that it not the type with the "U" clip that it together. That type is only for non derailleur bikes.