I yield the floor to Dondragmer on the color issue, but...
I also recall reading the comment from the auctioneer at Bonham's... I wondered about it, but it seems to me that as an auctioneer (not an artist), it would be his duty to disclose any specifics about his
perception of the color to prospective bidders, and since those prospective bidders are not schooled in either photography or costumes, it is a fair guess that it would be best, from his perspective, to underscore that the jacket did not really look "black" up close - black doesn't always mean what people think of as "black" (just as with white incidentally)...
I also know from experience that although most people are not color-blind, these areas of color perception tend to get mired in issues of subjectivity because we all have different retinas and sophisticated tests show that most people do not perceive the same subtle shades in-between color families.
It is possible that this jacket is creating one such Rorschach effect.
I suppose that the point I was trying make (since this thread seems to be about helping fans recreate a proper #6 blazer) is that if you go into the challenge looking for a patch-pocket single breasted melton wool jacket with a properly sized boutonnière lapel, and boutonnière sleeves, and look for it as a "dark brown", hoping to find something that will look like what you saw on TV or in the photos, you probably will never find it. On the other hand, if your search criteria is inscribed as "black", you just may find the jacket.
Another way to frame the question is "were you to address a tailor or a costume designer, would you ask for a brown or a black jacket?" - "would you ask him to find the proper shade of black, charcoal, or "brown"?
Dondragmer and I both seem to concede that "charcoal" is a more correct term, and artists also use notions of warm gray, that vary up and down the Pantone scale to black. Every shade has a warm and cold hue and gray can travel all the way to black, going through a shade that is likely to be that of the John Michael of London design.
Another "for instance" is that in advertising art and animation, warm gray and charcoal gray tones are used to color-in tree trunks, despite the fact that untrained artists think of a tree trunk as "brown"... I know this is all a bit technical, but costume design is indeed technical, and as Dondragmer points out, rightly, costumes designers never use the darkest shade of black for films because the darkest shade of black would never reveal any textures. All films use shades of gray to portray black. Quite often, costumes are made in different shades to correct for alternating lighting conditions, too. (It didn't happen with the Prisoner, apparently, which was produced fairly cheaply.)
Some scenes in the Prisoner, show McGoohan stepping outside in bright sunlight, and in those rare instances, you get to look at the jacket in its most unaltered image. There, you can see what its color appears in natural conditions and judge for yourself.
At the bottom line, for anyone interested in recreating the jacket, I wanted to illustrate that asking for "brown" or "dark brown" off the shelf, when discussing a melton wool jacket will not get you as close to the real deal as asking for black. Even though, true enough, you don't want the dark shade.
Dark Warm Gray, or Dark Charcoal, is probably the best description you can give anyone tasked with finding the right color for you, but understand that if you score "brown" your jacket will not look anything like what you are after, even if you've ticked all the other boxes.
We now come to the next level in the challenge: the piping.
I checked-out the link offered by Dondragmer (sewbizfabrics dot com) and I do think that the foldover bias is a good option, but their materials have a unique weave pattern which doesn't match #6's braiding.
To me, the jury is out on where to best match the pattern of the fabric which in many angles looks almost like a gros-grain horizontal pattern.
In Europe, I found a couple of samples which look close, but it is hard to tell exactly what was used in the TV series - here are some examples (They are not "foldover" but the foldover feature, though seemingly convenient, may restrict choices considerably)
-- In my view, it is important to look for a woven pattern which generates a horizontal motif when positioned properly.
This recent discussion has made me want to stick my neck out to locate an ideal piping, and I will post again soon, in the interest of helping others who may want to make a Prisoner jacket, if I feel I have found something to offer in addition to Dondragmer's links.
The samples (above) show various finds displaying levels of "off-white" from cream to bone, and "ecru".
The strip on the left comes closest in terms of pattern. The second strip is "grosgrain" which gives off a pattern similar to #6's although it is not accurate.
The other 3 are cotton braids. Also close, but no cigar... (More to come, later, as I get closer to the correct braiding.)
Below is a better look at the weave/pattern on the braiding from the series: