Yes Biz black chrome certainly exists. Product of the 60’s and Aerospace industry of which FN was right into at the time. So guess they could certainly have tried on barrels. It is lot more grainy than a bumper finish. It has to be a triple coat with copper and nickel and the chrome itself alloyed to get the desired black , depth and sheen. It would have been expensive and high tech for the time.
Sorry that you Australians went through such a thing. I believe the US would have a 2nd civil war over such a thing I would deeply regret leaving the planet that way.
I won’t hijack Biz post anymore but will put something in the political area on forum here in future. Then we can all have a good discussion.
Look at page 81 of S&V it has a serial number example. SAC 4 2277. Indicates a Super Allege Chrome Type 4 engraving pattern
yes I was relieved and I was afraid to open the package. Was the gun all rusty or did someone tamper with it.