According to the archives of the Kanes merchants, the city of Kuburnat was located at the exit of the narrow passage (or Sukinnu road) towards Durhumit (Gojko Barjamovic in "A Historical Geography of Anatolia in the Old Assyrian Colony Period") . So an enterprising merchant has accompanied 41 textiles from Hurama, went through the narrow passage, found himself safe at Kuburnat. After payment of a local tax, he shipped his goods to Durhumit.
A proximity with the country of Tahruwa appears in two other letters which trace a woolen reception at the Tahruwa country and payment for the wool trade representative in Kuburnat. The performer did not find the merchant at Kuburnat (because in fact he stayed permanently in the land of Tahruwa) request to return to the country of Tahruwa to go to Hurama.
From Kubarnat, traffic was primarily intended to Durhumit, only the cities of Tukuptu and Hanaknak appear as alternative destinations.
The Universal geographical dictionary of Auguste Wahlen, in 1830, states that Calpe is the name of the small river that would have reached the Argonauts, and Kirpé, Kerpen or Calpe is the name of the village at the mouth of this river. This place is quite recognizable on the current town of Kefken on the north west coast of Anatolia, in the Bay of Kerpe.
In 1848, a French traveler in Bithynia, Eugene Boreas, have published which he had observed in Calpe - as Xenophon in 400 BC when he had goes through there with his troops from Heracleia – a port on steep cliffs in the east, and a beach to the west with a access of about 120 m wide, and a source of fresh water nearby. It also mentions having seen the remains of wooden sheds and ruins of a tower.
I think it is the ancient Kuburnat. This positioning is quite in line with the texts of the Assyrian merchants: it allowed a Black Sea route alternative on the one hand via the Bosphorus by land on the other to go to Hanaknak.
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My notes of veracity :
2000 years ago, Kefken was the classic Calpe: 4/5
4000 years ago, Kuburnat was the present Kefken or Kerpen: 3/5