More to the point, how can you find out which chip the phone has before buying it?
As someone who formerly marketed semiconductors, simple answer is - you don't!!! Those things are internal to the bill of materials, and a lot of things are sourced from multiple vendors. Like DRAM could come from Micron or Hynix or Samsung. Flash could come from Sandisk or anybody else. SSDs could come from Sandisk or Intel/Micron or Western Digital... Whenever any fabless company - which is what Apple is - makes any chip, they can source it from multiple fabs, multiple assembly houses, multiple test houses - in fact, for something as high running as the A9, that's what they definitely do. In fact, I'm surprised that Samsung and TSMC alone b/w them have the capacity to service Apple - I'd have thought that they'd need at least 4 fab sources for the A9