Welcome to SCF!
Several definitions from the United States Stamp Society's A Glossary of Terms for the Collector of United States Stamps
*Cover(s) - 1.) any intact envelope, postal card, wrapper or similar mailed item. 2.) the printed pieces of cardboard used for the front and back of traditional booklets. The Scott numbers identifying such booklet covers are prefixed with BC.
Denominated Postal Cards - postal cards printed by vending machines in selected locations during the early 1990s. Scott CVUX.
Indicium - 1) the stamp-like impression on postal stationery, 2) the imprint of postage made by a postage meter.
*Postal Card - a mailing card produced by the post office, as opposed to a privately produced post card. A postal card has a stamp-like indicium. Postal Cards were first issued in 1873. Since 1999 Postal Cards have been sold for 1¢ over face value. Scott numbers are prefixed with UX. See also Denominated Postal Cards and Stamped Card.
*Postal Stationery - a category of products which includes Postal Envelopes, Postal Cards, aerograms, wrappers, and international reply coupons.
*Stamped Card - the current USPS term for what was formerly known as a postal card.
Based upon the above, I would say that the correct location for this post would have been under the Covers section; HOWEVER, this spot is close enough!
Your card is either Scott UX1 or UX3 (both issued in 1873) with the difference being in the size of the watermark (90x60mm and 53x36mm, respectively).