Identify of Amplifier class?
Stage 1:  Differential PNP Cascode Pair, comparing input with output with a gain of 100.  (Q1,2,3,4)    

Stage 2: Differential NPN Cascode Pair (Q7,Q9,Q6) with compensation caps and an Active load (Q8) and crossover bias diodes.  High gain.   

Stage 3: Differential Emitter-Follower (Q10,11) with compensation.
Stage 4: Current-Sharing Differential Emitter-Follower Q12,13,Q14,15

When Vout= +/-Vdc/2 the transistors draw 50% power of load.  Class A partial Class B with lots of negative feedback.

Mid 70's power design.    

DC Stabilizer and crossover distortion has  improved since then with better linearity.