Thank you very much, Galium (and your friend!), that's really helpful!
I did wonder myself whether the figure 17 related to the year of a certain emperor's reign, because there is a similar set of figures on the front of the card, including the number 17, which have helpfully been translated, and they are a date earlier in 1942.
So that confirms what I was thinking.
I've also looked closely at the two lines, and it seems to me that the second line is largely a repeat of the first line, but slightly offset, and with one or two symbols missing. The bottom line being written more neatly than the top line, which to me has the look of a 'rubber stamp' about it, with the images being fuzzy and blurred, as though the ink has bled.
I wonder, now, what is the meaning of 'transfer of control' and 'station departure'? I wonder whether my great uncle was being transferred to another camp?
I do know he worked on the so called Death Railway. He never spoke of this to me, and only a little bit to my parents, virtually nothing. Must have been a terrible, harrowing time that he was lucky to survive.
Thanks again!