What we can tell from this card, with serrated edges and mailed in 1955 using a postage meter, is that it was a special mailing from the Tower itself, complete with commemorative red medallion on the reverse (probably part of the postage meter) and a special non-postal stamp saying “Souvenir de la Tour Eiffel”.  In other words, you only got this card if you went into the Eiffel Tower.  Grade: 1