According to the CEPT rules you have to use the prefix of the country from where you are operating. You also have to add if you are either portable /p or mobile /m. Usually you should not add any regional information like OH1, OH2, OE1, OE2, ...
For Finland this means OH/xxx/p. If you are operating from a different DXCC entity, you either will use OH0 or OJ0. So it's quite obvious that OH always means Finland and not some of the other entities.
Same with Australia. VK/xxxx always means Australia mainland. If you are operating from one of the other DXCC entities belonging to Australia you most probably will either have an own callsign anyway, or you will use VK9/xxx and you manually have to assign the DXCC entity.
So if the prefix is not in an exception list for a different DXCC entity (like OH0 or OJ0), it's always the main country (Finland in this example). I tried this out in some other logging programs, all resolved OH/callsign correctly. The same is valid for CE, CT, EA, HK, ...
I fully agree with EI9JU, thanks God you're out of rope
![Wink ;)](./images/smilies/icon_e_wink.gif)
73,
Claus, EI7JZ/OE6CLD