Ive had a few 'all black' English bikes over the years, I had always figured they were a war time thing.
Including one with a blackout set of Miller lights with a mail slot over the headlight and the rear light blacked out with a metal cover with only a tiny slit in the cover. The rear reflector was glass but painted black, as was the tail of the rear fender, it had been white then painted over in flat black

The bars, calipers, wheels, spokes, hubs, crankset, were all black paint with a few pieces being black paint over what looked like sand blasted chrome. The one bike came from a retired college professor who lived near where I grew up. He had moved here from England after marrying his wife, they lived in the house she grew up in. He rarely drove a car, he had a garage full of old bikes and old, small, BSA motorbikes. Plus a few Italian bikes and scooters he brought with him after the war. When he got too far up in years he started to let things go, I bought the one BSA bicycle and another older rod brake 26" Hercules with rod brakes. Both were full black out models.

Back then they were just old bikes, so they got used and abused. I sold the Hercules in the 70's and totaled the BSA in the snow one winter while delivering newspapers. It was one of three I destroyed delivering papers back then.

Somewhere around here I've still got the lights and generator off the BSA, I think I swapped out the slotted cover for a chrome one. Both lenses are glass, the headlight has a bullet point in the middle, with a faceted reflector.
The tail light never worked and got removed and hung on the wall, its still hanging on the wall in the shed outback. The battery got tossed, it was a leaky mess, sort of a an oval rectangular can about 10" tall that was clamped to the seat post. It held liquid electrolyte or acid which leaked out and ate up the BB shell over time. I removed it fairly early on and replaced it years later with 20 nicad batteries from Radio Shack that I made into a 6v battery pack. I still have all of it somewhere, I've been sort of waiting for the right bike to mount it on. It may end up on my '56 Burgers ENR.