Continuity mistake: In the scene on the pier with Toshiko and Tommy, the soldier from WWI, Toshiko is holding her hand bag but drops it when he picks her up. Immediately, the next shot she is holding it again.
Factual error: Owen resuscitates Tommy using a defibrillator. The heart monitor shows a flat line, indicating Tommy's heart is not beating. A defibrillator has no effect in this situation. This is a widespread error in many films and TV shows.
Continuity mistake: Gwen views a transparency of two Torchwood members from 1918. The words "Torchwood" can be seen behind them. When Ianto takes the transparency and holds it up, the slide is different: it contains five people and the word "Torchwood" is above their heads.
Answer: Several times during the episode, most notably at the beginning when the old grave is discovered, Tosh holds a devise that looks a great deal like the Sonic Screwdriver that she uses to determine the age of the skeleton. However, a search of Google images shows that it is not the same thing.
OneHappyHusky