Visible crew/equipment: After King Richard has been crowned, Blackadder, Baldrick and Percy return to their chambers and start cheering. When Blackadder says "We're safe, and I am a prince of the realm" you can see the boom mike move up in the right corner of the screen. (00:16:50)

Visible crew/equipment: After Blackadder has his haircut, the camera zooms in on his foot. He lifts his foot revealing a red tape marker on the floor. (00:21:50)
Answer: The closest we ever get to knowing his first name is in series 3, when he claims it's "Sod Off". Blackadder asks him in series 3 where this came from, and he replies "Well, when I was a kid, living in the gutter, I'd go up to the other kids and say 'Hello, I'm Baldrick'. And they'd say, 'Yes, we know. Sod off, Baldrick.'" The S in this series is likely a reference to that, but it's not addressed, and given this Baldrick is clearly different from the series 3 Baldrick, we can't draw a direct link.
Shay