How did u get to this conclusion?

You wrote

> A certificate confirming he did learn the job

What would that certificate be?

In Germany that would be a recomendation letter, pretty much valuable by most HR departments, and not showing up with one isn't really recommended, a shitty one is better than none at all.

Yea apprenticeship certification is what I have (Germany). It's a lot different from other countries apprenticeships and shows ppl "Hey that dude worked this job for 3 years".

College degree should also work as you usually gather some job experience during university.

What i not meant were specific certificates like the Cisco ones.

Even a letter of recommendation from a previous employer would count for me.