The outer plates were gold colored and drilled, I used these chains though the 80's and my last one is stretched beyond use so I made a chain whip out of it. I'd love to have a new one but the NOS price is too high to make the chain usable.

From 78 Regina Catalog:

Narrow chain for high level racing.  IN addition to the exceptional resistance provided by the << BC >> riveting of the bushes and the high quality materials, the 50 Record chain features an extreme lightness obtained through the special design of the plates and a lightening hole in all outer plates.