As Martin Tompa explained, the Heimatschein is a certificate giving the bearer the right ot reside in a community. An electoral register is something different. Its existence implies that the community is governed as an elected body,  and further that the person listed is empowered to  chose the members of that body.  In modern terms that's what citizenship means, and the criteris for voting vary from country to country. .  Austria became a republic after 1918,  but I am pretty certain that a 17-year-old wouldn't have been entitled to vote. .
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Eva Lawrence
eva.lawrence@...