IIIC: EK vs plain numbers?

[HuubL]

Perhaps this has been answered before, but I searched and couldn't find it.
I just acquired a Retina IIIC (body number 100356, lens number 6448310). I checked several numbers of IIIC bodies and lenses and found that roughly they have corresponding orders, that is, low (early) body numbers have low lens numbers, the highest (latest) body numbers have the highest lens numbers. Mine seems to be the youngest of all 20 or so IIICs present at the moment on eBay etc.

Now some bodies have EK serials with numbers that do not match the ones that are plain numbers. I guess EK stands for Eastman Kodak.
Why are some IIICs EK and others plain numbered?

 

[nparsons13]

Same question applies to the IIIc (type 21), Ausf. II, as well. I have one, EK 744117, with lens no. 5293753. Note that Chris Sherlock doesn't have any EK numbers for IIIcs in his table of Retina folder serial numbers (http://retinarescue.com/retinaserialnumbers3.html). But the lowest EK number he has seen for the IIIC (type 28) is EK 756296.

I also have a IIIc Ausf. I that doesn't have the EK: 657347 with lens no. 4826878. That's within the range that Chris shows for the IIIc.

 

[VictorM.]

Here's a page from the IIa Manual:

 

[ZeissFan]

That's what I had heard - what is written in the photo of the camera manual page.

 

[nparsons13]

Good to know, Victor! Thanks for the info.