[ London Times ]
This newspaper, most correctly known simply as The Times, began publication in 1785 and continues to this day.
The edition of May 12, 1851, carried FOUR consecutive "Newf for sale" ads, although only one references the dog's color — black. All four may be seen in the image below.
FOR SALE, a BLACK NEWFOUNDLAND BITCH, 18 months old. To be seen at 19, Salsbury-street, Strand.
The amount specified as a minimum price in the second ad, 20 guineas, is equivalent to just under $3,000 US in 2020. This is the highest price I have yet seen being asked for a Newfoundland. Notice that the fourth ad, also for a 15-month old Newf, asks only 5 guineas, about $740 US, and that price included a kennel.