The c370 was the other bit. Nothing else. Looks like someone decided to include it on a whim. That said the cardboard box while a Scubapro branded box appeared to be either recycled spare box lying around because it had a white tape with handwritten note “converted to DIN”… not sure if the piece I got was originally yoke but it looks fresh and as DIN as a DIN can be…
Somebody at the place you bought your regulator kit is looking for their missing HP spool now. Probably somebody is getting fired for shortage in inventory. They are going to lose their livelyhood and probably end up homeless on a street corner begging for food and eventually turning into criminal life stealing HP hoses with gauges from tourist divers.