Montenegro, WWII Occupation period:
One great set overprinted, and very-very high value in catalog.
It is year 1943, overprinted in black "Nationaler Verwaltungsausschuss - 10. XI. 1943", full set in 10 values, and printed just in 1000 sets.
Naturally, for this period, and low quantity printed, exist lot of fake/forged overprint, as effort to make it available on market and yes, to make some money in wrong way!
It is very suggested, if You decide to complete this WWII period, to have this set properly examined and certified, just to avoid to pay high, for something that is not "as need to be"!
If You don't have any possibility to have this set certified, it will be very preferable, to have it at least, examined by someone who specialized in this field.
So, I mention that it is high catalog value, because Michel catalog, that have it under number 10/19, in mint, nh condition
valued at 7800.00 euro.
Enjoy Christmas gift, and take it to someone who "Know What Philately Is"!