Seller says "...missing magenta that makes the legend and value purple".
That could describe modern stamps printed using four-color process printing, but that's not how #832 was printed. It's an engraved stamp, with a plate for the black portrait and another to print the purple border.
Huge batches of ink would be mixed for each color, with ink supplied to the press as needed, and there would be no way for a small amount of stamps to be printed in a different color - the seller suggests "at least a pane or portion exists". No blending or mixing took place at the printing press to achieve a color.
Now, with modern stamps, a fount could run dry of ink, or a fold or stray piece of paper could interfere with the printing process, and a color COULD be omitted, and examples can easily be found for sale on
ebay.
But this stamp could not have resulted from "missing magenta".
Hard to tell from the auction photo, but it has a bleached appearance - there seems to be a bleed of red pigment into the paper, and the postmark looks washed out too.
Not everything gets listed in the Scott catalog, but a #832 printed in blue would have a major listing.
It is possible to get a certificate for #832c, which was a color variety created in 1954, printed in red violet and black instead of the original purple and black, but - big deal. Because, as mentioned, the colors were blended in huge batches, the color variety is common, and was valued at $6.00 in Scott Specialized (2010) in mint condition, $1.00 less than the original variety. And Used, both show a catalog value of the minimum, 20c.
I'm just saying...
-Dunc
PS: I see the seller ended the listing.