Tsujigiri, good to have you back! I hope I didn't sound overly pushy about the screwdriver issue; I was simply gratified to see the good screw heads on your gun and I guess I get rather protective (even when the gun doesn't belong to me
(By the way, if you are ever in the market for a basic and not-too-expensive gunsmithing screwdriver set, try the Pachmayr one available from MidwayUSA:
It's the one I have and it takes care of most common screws.)
The reason that I think your gun is probably a .25 ACP rather than a 5mm is that I have been compiling serial numbers of Clements (and many other pocket pistols) for some time. I note that on Gerhard Schoenbauer's vest pocket pistol website (http://www.vestpockets.bauli.at/archiv/archiv.htm
), his Clement 1903 is listed as a "late model" - which, after reading his description, I take to mean that it is a .25 - and the serial number of Gerhard's gun is 9828. The serial number of yours appears to be 9981.
Out of 7 or 8 1903 Clements listed in my database, the highest serial number is 10194. So, even though I don't have all that many examples to judge from, I'd say yours is very much on the later end of things.