[MRM]

Steve, the leaded windows on top are called divided light leaded windows. What that means is that each section of glass is truly a separate piece of glass that is held together by the lead - all of the lights are divided by the lead. You can buy windows like that, but they cost a fortune and are practically hand made.

What is more common today is lead windows with "simulated divided lights". What this means is that the glass in the window is all one sheet of glass with lead imbedded on the top and bottom to simulate the appearance of truly separate "lights" or pieces of glass. The performance of simulated divided light windows is actually better, because there are fewer joints and they're machine made. Good architectural quality simulated divided lights will look like real old fashioned hand made leaded divided lights.

Muntins are the removable wood things you stick inside a larger window that make it look like you have divided lights.

Mulls or mullions are the joint between two windows that are joined in the same rough opening. The top windows actually aren't mulled because they have their own rough opening. There is framining around the windows, so even though they're right next to each other, they aren't mulled.

The lower white vinyl window you posted also aren't mulled. It looks like that is a sliding window that is one single unit. In other words, the window is built that way at the factor with the frame and two sash, rather than being separate windows, each with their own frame and sash that were joined by a dealer or installer. But from an appearance perspective, that is what a mulled window would look like.

I would look up the web sites of Andersen and Marvin windows and see if their architectural series include lead simulated divided light windows. I'm sure Marvin does. Andersen might. Then just do an internet search on leaded windows.