The only patient data I have is that this ECG is from a 73-year old man.  At the request of the site administrator (Dawn Altman), I'm posting this ECG because there isn't one quite like it in the Guru's archives.  Some readers will recognize it as one I recently posted on another website.  This one lives up to the title of "Challenging".  I'll make the same general statement I did on the other website:  You'll need to make careful measurements with calipers on this ECG to come to the correct interpretation.

These are two 12-lead ECGs that I performed on two completely different patients several years apart. 

Patient's clinical data (Top ECG):
57-year-old black man

Patient's clinical data (Bottom ECG):
67-year-old black man

Are both of these ECGs showing the same rhythmic pattern?

I performed this ECG earlier this year in an outpatient clinic.

Patient's clinical data:  85-year-old white man; asymptomatic. 

Questions?
(1.)  What rhythm is this tracing showing?
(2.)  What clue/sign is used to differentiate between the two anomalous beats (i.e., 4th and 6th beats).  HINT:  It's named after a part of a certain animal's anatomy.

Patient clinical data:  68-year-old black man.

Question:
(1.)  What "pseudo" clue in Fig. 1 clinches the source of the mechanism seen in Fig. 2?