@James how can you tell a blackhole made out of antimatter from a blackhole made out of matter?

Question: @James how can you tell a blackhole made out of antimatter from a blackhole made out of matter?
- Keywords:
  antimatter,
  black hole,
  matter
Asked by Lone Wolf to James on 9 Mar 2017.
- James Harpur answered on 9 Mar 2017:
  
  You can’t.
  
  They would look the same as long as they were the same size and speed. Main difference with antimatter is that the electric charge is flipped but the mass stays the same as its partner.
  
  Nice question

Question: @James how can you tell a blackhole made out of antimatter from a blackhole made out of matter?