,the soldier in the foreground had installed the barrel band of his M1 Carbine upside down. Trivial I know and quite possible
Actually its not possible to install the Carbine barrel band upside down. Its possible the artist had seen a carbine who's lost or broken barrel band had been temporarily replaced by the mid stock band of a Mauser or arisaka. A poor fit but doable.
The Red Chinese and North Koreans used a mix of bolt action rifles, captured Arisaka, Chinese copies of the Mauser export model and the M1917 Enfield converted to 7.92X57 Mauser cartridges. They also converted many Arisaka rifles to 7.92X57.
Since the story takes place in WW2 Europe a Mauser band is more likely.