+1, it does look like it is for internal wiring. However, since it's not a grand touring bicycle, I suspect it's not a factory installation for lighting but a DIY for a computer cadence harness.

The New 600EX group, if original, would place it 1986-1987 and firmly mid-range. Most likely Asian. Probably a Tange #2 or Ishiwata equivalent tubeset. The chrome fork and solid paint reminds me of Bridgestone from this era. We may be able to tell more form the serial number, if you have it.