If only it were still on cover ...

2½-fr William IV
Official

9 May 1912Colmar-Berg
Bridge & Bar cds

Grand Ducal Chateau at Colmar-Berg

Fine used stamps evoke fantasies of the covers from which they were removed.  That's especially true when the cancel is that of Colmar-Berg, where much mail from the royals originated! 

The high denomination official stamp shown above might have franked a money letter sent back to Hohenberg in Bavaria, seat of the Nassau-Weilberg dynasty (such as the one shown below).  Of course, we'll never know for sure.

8175-Fr Money Letter

10c, 12½c, 62½c & 2½ Fr

Marie-Adélaïde Officials

Colmar-Berg, 6 Jan 1917, to Wiesbaden, 8 Jan 1917
Censored in Trier

From the Secretariat of
Grand Duchess Marie-Adélaïde

Correctly rated, thus:

Postage (20 g-250 g letter to Germany) = 30c

Registry fee = 25c

Money Letter fee (10c/300-fr) = 2.80 Fr

Total: 3.35 Fr