PS Audio Delta 100

I have a PS Audio Delta 100 powering my Magnepan 1.4s. Looking into the construction of the amplifier by displaying Google Images, I find most Delta 100’s have different architecture than mine. I wonder how many versions are there? What was the company trying to accomplish by so many redesigns? The only online image of a Delta 100 that matches mine was found on a South Korean used hi-fi market site. 

https://photos.app.goo.gl/SsBZ9sQZgRm7vTrj7