Help to understand old discrete mic amp design

Found this old Mic amp design and i'm not 100% sure about the function of the output stage. Mostly seen the output transistors biased with diodes instead of R10. C6,R10,R12 looks like a bootstrap with the R12 bias resistor used as a part of it, is this to save components or is C6 there for any other reason and it's not a bootstrap ?