Helmet stamps - makers names

[Danmark]

Hi guys ( and gals - although I think we scared them all away? )

I know a 'little bit' about helmets .... but here is a question about a feature I don't know - and maybe our experts out there may be able to answer it. Not earth shattering by any stretch, and doesn't make or break the hobby,but interesting nonetheless I feel.

The helmet factories stamped their initials in capitals ( ET, SE, Q, NS & EF ) and during the war ET changed to ckl and SE changed to hkp ( codes to protect the identity of the factories )

1) why only ET & SE? was it the capacity of the factories ... or their location, or vulnerability to attack?
2) Why are the "codes" in lower case ( there are some upper case CKL exceptions but not hkp )

...just wonderin'?
Dan

[MAP]

Not sure why some changed and some didn't. Would be interesting to hear if anyone does know.

[Kateri]

The lower case 3-letter codes seem like they should have been the norm,aligning with weapon and equipment codes.I think we should have been seeing them on a lot more helmets.
Why not?
Maybe the system of contracting to private enterprise meant the owners saw no need to remove their established marks unless compelled to.
I don't know anything about SE/hkp.
I know Quist only by their reputation for going their own way(Okay,you guys make some M42's in the corner over there.Just enough for the boss.)
qvl/bvl will always be the most interesting 3 letter codes ,and may remain a mystery.
I think ET/Thale was isolated from bombing and able to produce until demand was satisfied.
CKL and ckl are both there enough from the start of the the changeover from ET on the line that it looks like what was stamped depended on what was available to stamp.
I don't have a history in metalwork like Dan but I have a few dodgy CKL shells and a qvl.
I particularly appreciate my ckl60 with a lower case o instead of a zero.
Thanks Dan for posting questions from a production point of view.