Multiple sets of herring bone gears. I don't even know how these were cut and ground. Beautiful work.
If they are really herringbones - continuous teeth ? then they had to be made on either a Sykes or a Sunderland shaper. Probably have some video on you boob. On both of those one cutter supposedly makes the clearance for the other direction ... but in fact they both go solid into the vee, so they have to go pretty slow.
If they are ground tho, they have a space, normally called double helicals and they can be shaped or hobbed or even done some peculiar way. Hard part there is clearance for the grinding wheel. Those actually work better, except for in a pump.