I'm new too and basing on experiences with my own draft, I think it is still quite simple. Maybe you should have it be tied to a story or some sort? I was told that recently people would prefer a skip with some interesting stories connected to it.
Firstly: Congrats on putting a draft out here, I know the process can be pretty intimidating.
They are to not remove SCP-XXXX until they have looked at it for 5 seconds.
Why? What happens? Nowhere in your description did you provide a reason for this
SCP-XXXX's case measures 35mm from the 3 to 9 o'clock positions and 40mm from the 12 to 6 o'clock positions.
You don't really need to be this specific, just saying what model the watch is should be enough information, assuming it's a standard version.
Regardless of distance from the wearer.
This is a sentence fragment, you should tack this on to the end of the previous sentence.
Like karakaigara said above, this is an extremely simple and bare bones article as it stands now. It's a watch that teleports. And that's it. It need more to it in order to stand out. Try developing a story for your object. How did the foundation find it? Where did it come from? What other anomalous effects might it have? This is a good start, there aren't any glaring formatting or tonal issues, but you really need to develop this idea further before it'll be ready for the mainlist.
SCP-XXXX is to be kept within a Rolex oyster style box
And should the box (holding SCP-XXXX) be kept in a Foundation Site?
If the box is open, and SCP-XXXX is attached to any personnel.
What do you mean here? That once the box is opened, the SCP is immediately attached to the one who opens it? Is the box a sub-component of the SCP? Why let researchers be directly involved with the SCP (Won't a D-class suffice?)?
SCP-XXXX keeps accurate time, which can be changed without causing anomalous properties.
What do you mean by "accurate time"? Accurate how? To an atomic clock? I think you are meaning, "SCP-XXXX's time-keeping functions is the same as non-anomalous watches".
SCP-XXXX will materialize on the questioners arm within 2 seconds of the phrase being said.
Put an apostrophe for "questioner's".
the thinnest part of the left wrist
A rather vague parameter. What do you mean by that? Everyone's wrists are not the same size.
After personnel wearing the watch have looked at the position of the hands for 5 seconds. SCP-XXXX will re-materialize inside of the box it was last placed in. Regardless of distance from the wearer.
Broken clauses. The three clauses should be part of a singular sentence.
Okay, you have the object. You need a story to make your object more interesting. One thing that struck me as a direction to develop would be:
When any male within exactly 100 meters of SCP-XXXX says out loud "What time is it?"
Given the very specific requirements here (male, 100 metres, specific phrasing), it seems to be a thing for a specific individual. Who is that person? Why would he need such a thing? Why is it now in the Foundation's possession?
That said, I do find the "exactly 100 metres" condition to be unrealistic an too specific. Maybe "at a maximum range of 100 metres"?
In addition to my comment, I also noticed that by saying any male, you raised some questions:
What if more than one male stand in its range of effect? Who will the watch choose or will it duplicate itself?