in the old days they would of used metal work brake presses and such to cut i imagine and so the metal work guys i have spoken to that i have shown these to said.
i found that with the cost of labour nowadays laser cutting isnt any more exspensive and in fact most metal work places didnt want to bother with doing them and wanted them laser cut if thy were to do the folds (unless you were to cut and make them yourself, but they often have that home made look to them then).
also some sheaths i have, have curved shapes on the ends of the folds and making curves or shapes is no more exspensive if laser cutting, so that is a small avantage . the other sheaths are just neatly cut square ends to the fold over lips that hold the film in.
as you say its not rocket science to make them, but i was suprised how i had to twist their arm to get people to agree to make them--in the end they are doing it as a sort of a favour. they seem to prefer to make things that will bring in more money and bigger quanities of work. i was pushing my luck when i asked, if and how, they would go about making the actual plate holders. they freaked LOL, and said no way, look at all those folds and such and that 'we are only doing these to get you out of trouble' haha (i was only curious as i have heaps already)
the metal work guys reckon that in the old days they must of had machines specifically for these things, holders and the sheaths. as most modern machines in common use will only fold to a minimum of 4mm, whereas many of the old sheaths have a 3mm fold. in the end the guy will have to adjust his machine and then hold by hand to try and get the smaller fold, he says he thinks he can do it because of the very thin material, which is a special order by the way (for me anyway) because most commonly available stock is .5mm and the origianal sheaths are thinner than that