With a few exceptions, unused stamps from before 1870 should not be offered without a competent certificate. Removed cancels are ubiquitous, especially on the 1851, 1857, 1861 and 1869 issues. Some stamps, like the one pictured by the OP may show traces of a cancel while others can only be seen under a high intensity multi-frequency light source. Occasionally, dirt or smudges on the front of an unused stamp may appear to be a cancel. Sellers who bother to get certificates for better stamps will almost always achieve higher prices while buyers will receive better value for the money. Sellers offering high value stamps without certificates at low prices assume that most buyers realize that clean certificates would be unlikely. Profitable transactions occur when unwitting buyers pay too much. The philatelic marketplace is built on trust. Sellers who disappoint should be avoided.
To answer the original question: Sellers should offer stamps with clear images, front and back, with complete descriptions. On
ebay, the Condition Description should be used. Many sellers are not aware that the Condition Description will display if the stamp, unused or not is marked "Used" in the Item Condition. At one time,
ebay supported Item Condition names "Unused" and "Used". When Item Condition ID values were adapted, the ID values 1000 for "New" and 3000 for "Used" did not fit the Stamps category and Item Condition was dropped from being displayed. The Item Condition ID = 1500, would be the correct designation for "Unused" if supported in the Stamps category. For now, marking all stamps as "Used" (ID = 3000) allows the Condition Description at the top of the
ebay description to display.
Many
ebay sellers fail to provide good listings because of bad images, incomplete descriptions or failure to find or disclose faults. Some
ebay sellers believe that they are politicians. Like politicians, stamp dealers are selling hope, but that does not justify telling a whopper. Repeated small profits over and over is better than an occasional large profit without repeat sales.
Finally, describing centering can be controversial. It goes without saying that applying a numeric grade without a competent graded certificate is likely to alienate potential buyers. APS StampStore takes the prohibition one step further by no allowing conventional use of stamp grading terms like "Fine" or "Very fine". As mentioned above, use of Scott grading terms may be a waste of real estate in titles or descriptions, but it so commonly done, that many dealers continue the practice for perceived competitive reasons.