The Tudor Black Bay is the diver with a snowflake hour hand and a bezel that is often aluminum or ceramic, depending on the year. People use the name for the whole family, from the smaller cases to the larger ones. This note stays on the parts you can see.
How it differs
It is not a Submariner. The hand set is the quickest tell: the hour hand is a square snowflake, not a Mercedes shape. The dial text says Tudor. The case has its own lug shape, and the end links are cut for that shape. A bracelet from another diver will not sit flush just because the width is close.
Bezel inserts age in different ways. An aluminum insert fades and chips. A ceramic insert keeps its color and shows a hard scratch if it is hit. Write which one you see. The crystal on many of these watches is domed, so the edge catches light before the center does.
Common mods
Owners swap bracelets, and they swap bezels. After a bracelet change, press the end link into the lug and see whether it rocks. After a bezel change, the pip at 12 should line up with the triangle on the dial when the insert is seated. A crystal swap should leave the dome even. Hands are replaced when the snowflake lume no longer matches the plots on the dial. The movement, once the case is closed, should run with a steady seconds hand.
What to check on a used piece
On a used Tudor Black Bay, check the bracelet end links where they meet the case, the crystal over the dial, and the movement. Turn the bezel through a full circle. The clicks should feel even. A dead spot is a note about the click spring, not a story about the rest of the watch.
The notes for those parts are the bracelet, the case, and the movement.