In sacred art of this kind, there is a certain code that is conventionally observed to identify the four evangelists. Matthew, Mark, and Luke are shown as mature men with beards, while John is a beardless youth. I enlarged your pic as much as I could and all four seem to have beards. Also, we would expect Jesus to be differentiated in some way, such as a cross marking his halo. I didn’t detect any sign of that, either. Can you see any sign of those things on the crucifix itself, perhaps using a magnifying glass?
[Edit]
I just saw @Stephen_says’ post. Yes, I’m sure that must be it. The eight loops (if that’s what they are) on the sides of the cross are identical, apart from everything else.