Thank you for all the fast replies so far!
I am not su much worried about the necessary modifications.
I agree it should be no problem to look at the pcb and see if those had been performed.
The instrument has no fan, i opened it once already to take a peek inside. when i´m back home i will make some pictures.
Thanks for the link to xdevs.com, that was already in my bookmark list. Very detailed and informative site!
I am planning to renew the capacitors of the power supply.
Regarding the calibration i think you are right, it should be cheaper to have it calibrated by a company nearby. Or maybe find somebody nearby with an calibrated meter with sufficient accuracy.
As i had no idea about the prices i was wondering how much keysight would charge for that job. So i went to their website and tried the online form. But they are asking for a serial number. I will contact them by mail and explain my problem.
My biggest concern is that the serial sticker/plate did not drop off by accident. There is some probability that it was done for a reason. That is why i asked the seller about the serial number and proof of ownership.
He did not answer yet. Don't know what that means!
Actually i feel a bit stupid because i should have checked the serial right away when the meter arrived.
And the ebay description did not have a picture from the back of the meter.
Lesson learned!
Thanks so far
joerg