This is a rather interesting cover that was acquired recently. It was supposed to be sent from Nagoya in Japan to Kuching in Sarawak via Singapore but somewhat took a different and a very much longer route.
It was postdated at Nagoya as 11.4.17 using the Japanese traditional date system. Japanese in common with Chinese reads from right to left and so this translates as 17 April in the 11th year of the reign of Emperor Yoshihito in the Taisho era. This era began in 30 July 1912. So the conventional date of posting in Nagoya would have been 17 April 1923.
It arrived at Jesselton (D13) on 20 May 1923 and then transited at Labuan on 27 My 1923 ( D10 time code D) before arriving at Kuching on 6 JUN 1923 (D17). The whole journey took 7 weeks which was much slower than mail from Europe. It probably would have taken about 2 weeks going via Singapore.
The strange thing is there was no regular boat service between Jesselton and Japan. A Japanese ship called on Sandakan monthly and also the Eastern & Australian line dropped by Sandakan between Australia and Japan. It was quite possible this letter passed through Sandakan but did not received a backstamp. The reason why this route was taken remained unanswered but it should be a rare cover in this instance.