Actually SECC is a Japanese (JIS) standard for steel. SECC is the top grade of steel you will find in computer cases except for the few that still nickle plate their chassis. I'm sure you can locate the Japanese standards site if you need more info. 1.0 mm is the thickest steel I've seen used in computer cases, 0.8mm is more common - any thinner than that and I'd be leery of it.
SE= Zinc Electroplated Steel, C= Cold Rolled, C= Commercial Grade...
SG= Hot dip zinc coated steel. " " (likely to be recycled tin cans...)
. Some aluminum cases I've seen have 1.2 or 2mm thickness...
Linkage
.bh.
There's the :sun: !