hmm, I also worry that it's too old to work.
Regarding the price, it's about 500, seem cheap as most amplifier is sucking my blood out 
From most integrated amplifiers I have surveyed, all so expensive , i prefer something size and feature as light as O2 amp 

Well, good things don't come cheap, especially if its a sought after make.
This a vintage from late 70's, capacitors likely dried or will dry up soon. Anything old needs some attention or restoration work for another lease of life. If can DIY, it'll be cheaper, otherwise factor in another expense for restoration.
These amplifiers use phenolic material PCB, can easily be damaged if not careful with soldering skill.
My 2 sen.
P.S. Just checked the schematic, headphone output tapped from speaker line. 

haha, sifu you can take to test first, me slow slow cari...coz i also not yet got a set of bookshelf speakers