Most of the Ray-Ban sunglasses have the size printed on the inside of the left temple .
These three numbers (52-18 140 for example) are written in millimeters and match : the lens diameter, the brige width and the length of the temple.
Small ? Large or Medium ? It's hard to tell ! These numbers match the lens diameter. The lense diameter give us a good indication on the total width of the frame. Two glasses with different lens diameter may have the same total frame width (Aviatior 58mm width = Wayfarer 50mm width).
The «RJ» references are "Junior models" for children. It may also fit women with a narrow face.