Why do some HP calculators have springs inside?

[lvt]

(12-24-2022 08:07 PM)Steve Simpkin Wrote:  They were used to electrically connect the front metal panel to the rear metal back plate. This provided enhanced ESD protection to reduce the chances that static electricity discharges would affect the calculator.

That makes sense, sort of Faraday cage?

But I remember a 12C that doesn't have a metal plate at the back, the instructions are printed on the plastic. I'm not aware that calculators with front metal plate need shielding. I used to have a couple of Casio calculators with front metal plates but I don't think they have springs like this.

So was it mandatory or it's just the tradition to make the 12C more authentic to the past models?