It may be normal, early horsecollar BCs were often very small and the intent was to keep your face above the water since they were designed after Mae West type life preservers---get it--Mae West? The dual bladder unit I pictured is not that type, it comes below my natural waist, actually quite low thus keeping the center of lift , well, centered for a horizontal swimming position. Many also used a crotch strap to help keep them from floating up around your face. Since divers of that era had probably been trained with no BC and therefore understood weighting and wets suits were a luxury much less a dry suit their small capacity sufficed and little air was normally introduced into them preventing them from trying to float you vertical in the water or constantly be pulling up on your--well--I will leave it there. I imagine the unit I pictured only has about 15 lbs of lift, maybe a touch more, in the lower bag. The upper section being used for surface flotation or emergency use only. N
