300-day Journey to & from the Belgian Congo in 1902 -- a 'Philatelic Tragedy'

10c+10c Allegory Message-Reply Card (3rd series)

UPU-rate message-reply (double) cards can be the postal stationery collector's worst enemy or best friend -- your worst enemy if you lack incoming uses of the reply cards; your best friend if you have scarce incoming uses.

Well, while working on a one-frame exhibit of incoming uses of Luxembourg reply cards (and outgoing uses of other countries' reply cards posted from Luxembourg), I revisited this well traveled Allegory message-reply card with the unused reply card still attached.

Here's this double card's apparent three-country, 300-day journey to the Belgian Congo and back:

July 29, 1901 to May 25, 1902

• Alfred Beck, a student whose address is 5 Saarstrasse in Trier, Germany, writes to G. Kalber in Boma, the Belgian Congo, proposing an exchange of cards and stamps.  He dates the card 'Wasserbillig, le 28 juillet 1901,' and posts it on July 29, 1901 from Wasserbilling [large double circle cds].
• The card arrives in Boma, Belgian Congo [blue-green cds] on August 27, 1901.  But where is Monsieur G. Kalber?
• Auxiliary marks in French are applied:  'Retour a l'Expediteur' [at the bottom] and another at the upper left that I think indicates addressee unknown. 
• Boma, April 29, 1902 [black cds struck twice], as the card is now being returned since G. Kalber hasn't called for it. The sender's name and address has been transcribed from the message side to the front in purple pencil for return to Trier.
• Trier, Germany [bridge cancel], May 23, 1902.  Now the card is back to Trier, but the writer apparently isn't at 5 Saarstrasse anymore.
• Auxiliary mark:  'REBUT' [dead letter] returned to Wasserbillig [May 25, 1902, large double-circle cds].

So, while interesting, this story is really a philatelic tragedy.  If G. Kalber had returned the reply card from Boma, we might now have an even more interesting story -- a reply card returned from Africa. 
By the way, double cards returned from Africa are quite a challenge.  I show an uprated G.D. Adolphe card returned from Tunisia here.

The writer's message