Guess I am taking a top down approach. I know little here, there are several types of metal and several types of plastic? or only 1 plastic? different or same type 1 to type 2? Are all within a type interchangable? Then there is that metal knurlled handle on the end or is that a different item?

As I know...

There are different types of the complete crank:
with metal crank arm
- at least two different lengths
- without or with a white arrow
- hole for the conus pin on the left or in front of the crank arm (0 or 90 degree)
- with blank metal or red painting (for subtraction position)

with plastic crank arm
--- the plastic is called Delrin
--- only one type of plastic crank arm (?)

The position of the hole for mounting on the main shaft differs between the plastic and metal type - so it's not interchangeable. Also the knurled handle is not compatible because the axle is not exactly the same.

This has long stumped me...

Initially the metal cranks on those earliest units, both type I and type II, had NO arrow markings...soon however, the arrows were present on these metal cranks.

The plastic cranks, on both I and II have had arrow markings from the beginning and in all these examples, the angular orientation of the arrow appears consistent.

I've even placed a temporary arrow on my early type I to try and determine what purpose the arrow would serve during operation, but sadly have no clue yet.

Help...am I missing something??