RK05 classic computing trivia question

[tony duell]

> As a guess, something is either twice as small, or there twice as many of them.

The RK05F has a pair of heads like an RK05. It has twice as many cylinders, which are logically addressed as
2 physical drives. So the optical scale in the linear positioner (which is not part of the head) is different, and 
there are some minor differences to the drive logic boards.

The heads look very similar. The mounting arms/springs are the same. The head 'buttons' are similar-looking
white ceramic disks. Yes, if you compare them, the core width for the -F is narrower, but to recognise the
heads like that you either know them very well or have a pile to sort through and can see both types next
to each other.

There are no obvious coloured dots on the springs, or part numbers, or anything like that.

But there is one thing that is different. 

OK, I'll give a hint. There is no reason it has to be different, it is done for identification. And it is a 
colour.

> Either way, I could really use both -:)

Heads or drives?

-tony