The printer arrived today. It does the selftest, but the needles sometimes stick. After a few selftests this was resolved. Now I don't get any characters on paper because the ribbon is dry. The supplied spare one is dry also. So the next step is to get some good inkribbons!
To temporarily revive the ribbon I used some WD40 as stated on some websites and I can confirm that this does work!
Found these ribbons at the online Staples store. It's the same ribbon as for the Olivetti DM 100 printer. The Olivetti product id. is 82556. So I ordered three of these.