Re: Second Doctor's Sonic Screwdriver
And, as has been pointed out, it was the same prop Hartnell used on a number of occasions, most notably to open the TARDIS lock in the pilot episode, and to sabotage the Dalek detectors in the first Dalek story.
"Some days are better than others. They say that where I come from."
"Loudly, I imagine, on the day you left."
(Blake's 7 - Rumours of Death)