I collect Canada George 6th with my main focus on WW2. I know nothing about US postal history. I recently obtained this POW card from a prisoner in Canada to his uncle in the US.
It is not that unusual - except it is from a survivor from a U-boat - but I know nothing about the red US censor cachet. I assume it is common but there is nothing to say where it was applied.
If anyone could to point me to an online link like about these or supply any info. about it I would be grateful.