.The chess sets were sent out as escape aids in WW2 by M19 a branch of military intelligence tasked with helping POWs escape. In this case by hiding information etc in the tube where the pieces go. Not too much was known about M19 who were also tasked with obtaining intelligence from foreign POWs and anyone they thought was collaborating with the enemy and they used any means they felt was necessary often being accused of war crimes. This is going to make me have more respect for my travel magnetic chess set in future.