What is the correct way of writing two MSc degrees on a business card?
How about


  John Doe, MSc (Comp. Sci.), MSc (Sci. Comm.)


? (Then again, this could look pretentious. Proceed with caution.)

Unfortunately, the relevant Wikipedia article is not highly informative, and anyway it is flagged as "citations required" and specific to the UK:


  Where two different postgraduate qualifications with the same name
  have been obtained (for example two different postgraduate MAs from
  King's College London and University of Sussex), this can be indicated
  by using one degree postnominal, and the abbreviations of the two
  awarding bodies in parentheses, sometimes joined by the Latin "et" (or
  with an ampersand), e.g. "Jane Smith MA (KCL et Sussex)", and not
  "Jane Smith MA MA". However, when qualifications with the same name
  have been gained through different routes (for example an MA from
  Oxford University converted from a Bachelor of Arts, and a studied and
  examined postgraduate degree from King's College London these are
  listed separately with the institution only listed after the
  non-examined qualification (e.g. "Jane Smith MA(Oxf) MA", and not
  "Jane Smith MA (Oxf et KCL)").