That sure looks like a 63 GA. The 63 changes series field taps with a wire GSF to GSF2 is 3 turns per pole. GSF to GSF 1 is 4 turns per pole. GSF 2 to GSF1 is one turn per pole. So you end up with 12 turns on GSF to GSF 2 and 16 turns from GSF to GSF1 and 4 turns from GSF2 to GSF1. The 71 GA and 82 GA have taps on each pole piece to change Turns. If your in New Zealand, your stuff probably came from the UK. I adjusted a 3 car group and a service car on the Grand Bahama Island and their stuff came from UK. Everything was a mess from there,As your glaze gets stronger your compounding will get weaker with the increase in loop circuit resistance. If you run out of turns and still need stronger compounding, you can shift the ring a 1/16th off neutral and against the rotation will make it stronger. With the rotation will make it weaker. Very common to shift ring on a 63 as your control is limited. Can only do so much with the bedspring shunt on back of controller .