Does not sound like an overkill at all.

If anything, it is very sensible considering the grief and hassle that is
associated with making a claim or attempting to obtain compensation for
a lost or stolen article.

When something goes missing, it is bad news all round, both the buyer
and seller loose out. Any tips or tricks that minimise the possibility of a loss
are welcome!

Perhaps, your advice should be used as part of the 'how to send valuables
via courier or post' FAQ

: 1. Small box, watch inside securely with bubble wrap or other
: packing material. Tape seams.
: 2. Place small box in outer box, preferably at 90 degrees so the
: major seams don't align. Tape seams.
: 3. Wrap outer box in brown paper, to mask where box seams are. Tape
: seams and all edges to reinforce.
: 4. Photograph the whole package and send to buyer. They can then
: easily check for tampering.
: 5. If the buyer has the photos at receipt, they can check the box
: whilst the delivery person is present before accepting it,
: flagging up any problems immediately.

: Might seem like overkill, most go through easily, but it's a
: worthwhile form of (figurative) insurance.