Ref.6536 was a model produced up until around 1955 but looks as if it initially came with a variety of differences.
There were very few, and the initial model came with a Red Top, a non-incremental bezel, a white second hand and Red Depth, for example, rare detailing seen here and there. This one comes with Red Depth and a non-incremental bezel.
The special detail of these rare pieces also make these exceptional and likely to increase in value in the future, usually heading towards that of Ref. 6538 and Ref.5508.
This is because the same guard-less sub of 6538/5508 has been incredibly popular of late, and the degree to which something good has been unavailable. The crown guard of Ref.5512 with circle mirror dial of the is also unusually popular, and in a 2-line model is already more expensive than either Ref.6538 or Ref.5508.
When this comes up next, it feels as if it will be quite natural for 6536/5508 to gather a steady stream of attention, having previously been left behind by rising prices.
When compared together, the mood of the Ref.6536 with its gold hands is, for reference, still the better of the two, but many more dials that have a stronger fluorescent finish as mirrors can deteriorate, while the lustre of the Ref.5508 mirror dial retains its impression of being in good condition.
The thin-fit case of 6536/5508, as opposed to 6538/5110, is good for everyday use and a surprisingly important piece I think.
1956 ROLEX Submariner Ref. 6536/1