Looks like it might be a clever way of winding a 4:1 voltage balun to simplify the wire routing (or just straight up incorrectly wired). I'd have to see the connections at the top more clearly to be sure.
Regardless, seems pretty safe to assume it's a voltage balun. The quick way to tell would be to check it for a DC short between the terminals on the unbalanced (or balanced) side. If they're shorted, it's a voltage balun, and as such, not much of a balun at all. The choking impedance from these single core 4:1 voltage baluns is so low (usually <500 ohms) as to be nearly useless unless your antenna has low enough impedance that yo don't need the 4:1 to begin with. W8JI and K9YC have both done good tear downs showing just how awful they are for most applications. They should be considered an impedance transformer and not much else.
EDIT: drawing out the windings, it appears it is an attempt to shoe-horn a 2 core Guanella 4:1 current balun on to a single core. Figure 2 here shows how it would be accomplished with two cores, and the builder appears to have just decided to do a split winding on a single core, perhaps in an attempt to get the best of both worlds, good common mode isolation and a 4:1 transformation on a single core. In reality, I would guess this actually causes it to exhibit less than a 4:1 transformation, in addition to having little common mode suppression. It appears it would exhibit considerable shunt capacitance between windings, and depending on the core material, potentially a low impedance shunt path through the core.