that 3d model brings up a question I had. Does the screenused prop have an open chamber in the emitter, as pictured... or is there a rod that extends to the lens on the top?
Since this has already been bumped I figure I'll add my contribution.
Here's a shot from Nick Robatto's Facebook. You can see on the left one of his screen accurate reproductions next to the CO toy. CO is very close to the correct size and a lot of the details are pretty close, too.
Supposedly the sonic between the Wand Co. 11th and the sharpie is the screen used prop, but I can't verify it. All the pictures I've seen of the screen-used prop have a lighter crackle finish.
And here is the CO toy next to the Wand Co. 10th sonic reproduction, scanned from David Tennant's personal sonic.
(I theorize it's supposed to be the sonic we saw destroyed in the 11th Hour with added and rebuilt parts)
A day, maybe? If I remember correctly, the Doctor gave it to her the last time they were together, which was the night before she left for the library. I need to re-watch it.
I have been smart.
If you still want the measurements,
i checked the QMX artisan river sonic page ( River Song's Sonic Screwdriver - Prop-Maker Edition )
and if you look carefully it says that it is about 175 mm long (17.5 cm or 6.89 inches)
and because these were made by nick robatto and they are the exact size of the prop, these are good measurements