Hi friend ...
I suggest :
To be the most precise possible when to classify our cameras:
It would be necessary not to use any more the word "galvanized" .
The process employed here (and what I learnt in "60's",when I was technical student) is called "scratching": it allowed an excellent precision of finish of surface a time when we did not still use grindstones ot chrome for finish.
The tool employed for this work is called "hand scraper".
So, According with the philosophy of JL Princelle, we can see there, in the irregularities of the drawing on the metal, a touching signature of those who made these cameras
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For those who want to know more about it, look here: in particular look at the aspect obtained on flat surfaces of machines (precision, approximately : 2 to 3 microns)
http://www.usinages.com/le-grattage-t1158-135.html