REGARDING THE SPEEDLITE 600 EX-RT.....I HAVE NOTED A NON-RT MODEL...WHAT DOES THAT MEAN?

[digital]

It is not Radio Transmission capable, only optical. Did you want RT?   

[7D5D]

If you are referring to the 600EX (without the the RT), that model is optical controlled only like the 580 and 430 series and sold in markets (countrys) that do not allow Canon's radio controlled devices.  I'm not an expert in radio controlled specifications so I don't know what specifically it is that prohibits it.

[digital]

Here is a list of where they are allowed. I asked if the OP wanted RT because I read of people getting the non RT when they thought they getting the RT for a great deal. You have to watch carefully when you purchase on line like eBay. 

http://pixsylated.com/blog/where-in-the-world-can-you-use-canons-600ex-rt-speedlite/

[digital]

Well it is not allowed in Israel which is a place that has a wee bit of tension with the neighbour's so that kind of tells the story. I could be wrong but that is my guess.