Who will have won?

Collecting individual stamps is fun, but collecting postal items is even more fun. Especially when those items tell a whole story. For instance, I came across a postcard (or is it printed matter?) that was sent from Hellevoetsluis to Amsterdam on August 5, 1924. A few things immediately stood out. Such as the postmark on the 2-cent stamp (for the domestic printed matter rate from March 1, 1921, to July 1, 1927). A stamp that was used by the conductor on the steam tram (the "Moordenaartje") from Hellevoetsluis to Rotterdam. This stamp was used from 1913 until August 1961! But there is more to see. A small stamp with the letter G and the number 630. What was that for? In those days, every mail carrier had their own number, and before he went out onto the street to deliver the mail, all mail items had to bear his stamp. This way, it was always possible to check afterwards which carrier had delivered the mail and also with which order. The largest post offices had as many as eight deliveries a day back then. So the letter G was used for the second-to-last delivery.   But what was this card used for? We can see that on the reverse side. The card was apparently printed by the Dutch Chess Federation to enable chess enthusiasts to play chess with each other 'at a distance' in a simple manner. For a chessboard was also pre-printed. The chess pieces had to be marked with impressions of small stamps (black for black and red for white). A rook has apparently been captured by White! The white king is underlined with a pencil line. What will Black do now? But was this printed matter or a message by postcard? Was the Chess Federation right to print 'PRIEFKAART' on it for the rate of 7½ cents? Or was the chess player right? Whose turn is it?