I have been fascinated by this thread. The idea of a link to Eastern European nobility would have anyone asking questions, I suspect. Are you aware that the only reason that you are ever asked to prove you are a baptised Catholic is when you are about to marry in a Catholic church ? It was never normal for any Catholic church to produce a baptism certificate at the time a child was baptised, if it was still the ninteenth century. If you continued to live in the same area as an adult, when you wanted to marry, the priest could just look up your baptism in the church register. If you had moved away, the priest would write to the parish where you said you were baptised to check. This is why Catholic baptisms sometimes have the marriage noted in the margin.
It seems to me that the 1907 paperwork has probably all been produced in just this situation. It explains the reason that it is so many years after the event. It also suggests that Marko was planning to marry in an English-speaking country in 1907-8, so had to get the paperwork translated. The same documents could have been used years later for the marriage to a different woman, ie Norah Doyle.
Edited to add 15 mins later:
It would be interesting to find out when civil registration of births began in Croatia. When no civil birth registration existed, it was nomal, for example in Ireland, to accept a baptism certificate as a substitute. Could the 1907 documents relate to a naturalization for example ? What was the date of the New Zealand naturalisation referred to earlier ? Just some suggestions. I would still agree with jorose that a new translation of the Serbian document is needed.
