This postal card was sent from Fiume (now Rijeka).
Fiume is on the Adriatic coast about 50 km southeast from Trieste across the Istrian Peninsula.
Rijeka is a port city now in Croatia.

The postal card was a 2 kr.* denomination used for internal mail.
The card was cancelled with a FIUME CDS but was shortpaid.
It was marked with a bold T to indicate that postage due should be collected at the destination.

The destination was Geneva.
There 5 c. and 10 c. postage dues from the 1884 series in olive green with red numerals
were applied (Scott J23 and J24) and cancelled with two
September 23 GENEVE FACTEURS cancels.

Facteurs are carriers, so this stamp was both received in
Geneva and rated with the postage dues by a carrier.
The more usual practice would for this to have been done in two steps;
first by a receiving desk and then by a postage due desk.
The carrier credited the sender's domestic rate card for 2 Swiss centimes
and then valued the total charge at 8 Swiss centimes.
He then doubled this for the penalty and charged 15 Swiss centimes
(rounded to nearest 5 for convenience) and affixed the postage due.*

There is also a clear GENEVE CDS on the front.

I believe the blue pencil marking is '15' for the 15 c. due.

*Thanks to Roger Heath, Jim Whitford-Stark, and petrelet for helping
me better understand this receiving and postage due process.
Thanks to David Benson for catching my typo on the 2 kr. value.