Use one lamp and move the crystal under it. A flat crystal throws a broad reflection. A domed crystal bends that reflection into a curve that travels as you turn the case. Pits show up as tiny dark points in the reflection. On the lug, a polished bevel should carry the lamp as one continuous line. A break in the line is a knock that was buffed on one side only. You do not need a loupe. You need the lamp and a slow turn. Write the surface as you see it. Do not convert the observation into a grade, and do not compare it to a piece in a display box.
How it differs
For the Cartier Santos 39 8 Mm, compare the diameter you can measure with the length from lug tip to lug tip. A wide bezel can make the dial look smaller than the case. Keep the comparison inside this case idea.
Common mods
On the Cartier Santos 39 8 Mm, people change the insert, the bracelet, or the hand set. Name the one part that was changed and leave the rest undescribed rather than guessing.
What to check on a used piece
Check the clasp position, the end-link gap, and whether the hands pass cleanly on the Cartier Santos 39 8 Mm. Write those three and ignore the sales line. These notes are not authentication and not a shop.
A library page is written by Watch Notes. A photo post is one person’s notes. Neither authenticates a watch, offers it for sale, or speaks for the name on the dial.
Same reference family, additional case notes for Cartier Santos 39.8 mm. Measure across the bezel and from lug to lug, read the engraving, and compare the bracelet or strap with the lugs. People change the clasp, the crystal, and the bezel insert.
What people change
On the Cartier Santos 39 8 mm, people change the bracelet, the case, or the movement.