How do you add two independent master's degrees to your name? Assuming you add one master's degree (Master of Science) like that:
FirstName LastName, M.Sc.

What is a proper way to add two independent1 master's degrees (both Master of Science)? Do you just add them both to the end?
FirstName LastName, M.Sc., M.Sc.

1 independent: Different universities, different fields, 2x 120 ECTS = 240 ECTS in total. Not the result of a double degree program.

Just to be clear, I am not looking for recommendations, if or when I should decorate my name with academic degrees. I do not even plan to do it on a regular basis. Even in my country, you don't do it very often. But if there is this one single time in my whole life where I should do it, then I want to do it right. That's all I am asking for: Are there rules or good/best practices on how to do it with two M.Sc. degrees.
Example situation: If you get mentioned on someone else's thesis as an examiner or as a supervisor the names will be decorated with degrees. A german doctor with three doctoral degress can either be Dr. Dr. Dr. FirstName LastName or Dr. mult. FirstName LastName. This example shows two possible rules:

You can stack titles/degrees. Just add as much as you have. That's from where I derived FirstName LastName, M.Sc., M.Sc..
You can condense - at least multiple doctoral - degrees by adding mult. to the mention of one single title/degree. I have never seen this in combination with other degrees.
Unless you are in a place that regulates academic titles, you can do pretty much as you please. But you could qualify each with the specific field or university if you feel the need to list both.

FirstName LastName, M.Sc.(Basket Weaving), M.Sc.(Basket Burning)

Distinguishing by university, rather than field will probably confuse people, thinking you have two masters in the same field. Qualifying with both is probably too unwieldy.