Germany, Scott #302, used(o), 1923, issued November 1st, Inflation Era, 20 million marks, rouletted 13, on medium white wove paper, 'networks' watermark (Scott watermark #126), ultramarine, Scott 2019 catalog value: $300.00, off centered, stamp has four cancel strikes, each a circular double-rimmed, clear middle space for date/time, socked on the nose cancellation, all well covering the main image (from the cancels, we can piece together "[DUIS ... then BURG, and 7 11), from the information seen and from the spacing of the data relative to the logical centering of the cancels, and from the knowledge of the issue of the stamp to be November 1st, 1923, the post mark is most likely Duisburg, November 7, 1923, and Duisburg, in the wealthy Rhineland near Dusseldorf, would be a city where people, in this period of Germany's hyperinflation, could accumulate 20 million marks for a mailing, sound back, hinge remnant, good perforations. This is not a 'bait-and-switch' offer. The stamp you see will be the stamp you receive.
At catalog value $300.00/used and 55¢/mint, you have to worry about a forged cancel; however this stamp has three indicators that it is likely authentic: 1) it is distinctly off-centered, 2) it has a four-strike cancellation, and 3) it has full circular cancellations with mailing details regarding post office and mailing date. As a collector of used stamps, I have been studying these forged cancels for years both with Germany and Italy. In most forgeries, the forger selects nicely centered mint stamps, and the forgeries have light, off-center cancels that lack post office and date of mailing details, and it is highly unlikely that a forger would render a four-strike cancellation So, I think this stamp has been correctly postally used in the period of issue.
Please review my terms of sale. If you are not ordering from the United States, there is a $US1.20 additional postage expense that needs to be added to the price of the stamp, plus a certified mailing fee that varies by country of destination, but is approximately $4.00 per $100.00 of insurance. Thus the cost of mailing and insurance for this stamp will be about: $5.20 for most customers outside of the United States. If you are ordering from the United States, there is only a $US0.55 added postage expense, plus a $3.50 certified mail expense, total: $4.05. Also, if you make additional purchases from my offerings, they can all go in one mailing at no extra expense for the added purchases. If not satisfied, return the stamp to me at your own expense, and I will refund the cost, but not my postage to you. If the stamp is not as described, I will refund the cost and reimburse you for postage both ways.
By way of reference, I am an American Philatelic Society member (195176) and an American Stamp Dealers Association (ASDA) member. Thank you for looking, and I hope this is the perfect stamp to fill that gap in your collection.