It sure looks like 11/44 to me too! I wonder if the scratchy penciller had an off day & car crashed a 'D' of the serial prefix into the second 4 of the 44? I have just this afternoon been working on an A prefix 8/44 receiver. Could the serial possibly be D 875?
If it is 11/44 it would make it a first year of production rifle, but much too late to be a prototype.