I have found these numbers on the Koken Barber Chair that I have.
can you help me with the year time frame it was made.
The numbers on it in different areas are as follows.

1) 5 2 7 N B A
2) 5 2 8 N
3) B 1 5 6 0 3
4) 4 0 D and 4 3 == both on Head Rest
5) 3 5 4 P M = Pump Arm