Today it's dense in this band, but you have to leave the frequency of the UTIL station alone: network costal meteo USB 1785,1782, 1728, 1710, 1692, 1674.
At 1680 some Greek is trying to break through hours of digital transmission.
There is, perhaps, something of a "band plan", from personal observations:
The Russians are usually on 1700 to 1800 KHz. (You can see their bad VFOs drifting and FMing on your SDR waterfall display. Clean signals do not seem to be their priority.)
The Dutch are often (but
not exclusively) on 1610 to 1650 KHz (roughly).
The Greeks are often 1610 to 1750 KHz. In the mornings they tend to gravitate more toward 1650 to 1700, and especially 1690 KHz.
The Serbians are in there wherever they can fit in and not get stepped on by the other three, especially the Greeks and Dutch running multi-kiloWatt TXs.
I think that these guys aren't paying much attention to who else might already be operating on a particular frequency. If a Greek station wants the frequency, they take it because they feel that their signal will overpower the Dutch station already on there within their local listening area. The Greeks stations don't seem to care about reception outside their area, although they certainly can be heard in northern Europe at night.
On the other hand, the Dutch stations seem to cultivate reception reports from outside of NL. They live in a small country so when you run 10 kW, you are going to be heard outside of the Benelux pretty easily.