I am a European master student and recently accepted a PhD position (Computer Science/Machine Learning) in a German speaking country. I did multiple research internships in Europe during my master's, and I would argue, they define me more than my actual degree. To "onboard" with my university, the HR wants to know if I have relevant work experience (to determine my salary) and to back them up with e.g. what in German is called an "Arbeitszeugnis" and translates to a recommendation letter or reference by the employer. It was then that I realized that except for my signed contracts, I do not have any certificates or "open" reference letters from my research internships and also that in more non-academic or not so highly competitive settings, reference letters could be asked to be sent with the application by the applicant. Therefore, if for any reason I would drop out of my PhD, I think having an unaddressed reference letter by hand could come in favourable.
All my internship supervisors agreed to act as references for me and I have listed them in my reference sheet. I have no problem asking them to quickly write an official document certifying that I worked as an intern within their group, which will be enough for my university. Asking for an unaddressed recommendation letter, however, conflicts with my strong perception that in the academic world showing / giving recommendation letters to the applicant themselves is regarded as highly non-professional (the reference may not be honest!). At least, this is what I gathered from the attitudes of the professors in the research institutions I worked in and hence, did not at all think of the possibility and necessity of ever asking for such a letter.
Therefore, my question is, do you think it will hurt my reputation if I would approach my supervising professors and ask if they could send me an unaddressed letter of recommendation for later usage? Or, do you think it won't be necessary to have such letters of recommendation if I acquire a certificate of my employment, because I can always refer to the contact details of the professors in my reference sheet. As I am the first in my family to obtain university level education, I am unsure if I maybe misinterpret the "business world" (particularly in Europe, but also the US) and employers at the master or phd level will never ask for direct letters of recommendation?
One could argue that it is premature to ask for such "open" reference letters and I may only ask if I really need them. However, I am talking about research internships one and three years ago and hence, think I should ask rather now than later, before all my work will be "forgotten".
I would very much welcome any kind of feedback / opinions from any knowledgeable person :)