How does that work, then?

My washing machine broke down about seven years ago.  It was, then, itself about fifteen years old.  I wanted one exactly the same: after all, despite the twelve different options on the rotary programme selector and the five mysterious pressable buttons, I'd only ever used it for three purposes: whites, coloureds and occasionally delicates  (when I couldn't be bothered to handwash a pullover). 

So when the old one broke, it was dead easy.  I went to John Lewis and said: "Can I have a new Bosch Lavamat 3100 please?"*  The salesman didn't bat an eyelid.  "I'm sorry sir, that's a very old model.  Obsolete, in fact."  He frowned.  "What you need is the Bosch Lavamat 6100."  My heart sank.

He showed me one.  "Hang on," I said.  "That's pretty much identical to the 3100, isn't it?"  He smiled.  "Outwardly, yes.  Of course, the internal technology has been radically -"

I cut him off.  "I'll take one."

He smiled again.  "Very sensible, those Germans."

Thanks to Z for opening up this rich vein of potential bloggery. 
* I may have made up these model numbers.