The "Advertising" marking was used exclusively on the expedition film advertising post card. This marking in found primarily in red, but a small number of the post cards bear the marking in black (M3b). All of the cards that bear the M3b marking, without any other expedition markings, were mailed from Calcutta, India after the expedition return during the October time-frame.

   The advertising card was created by Capt. Noel, who was tasked with making a documentary film of the 1924 expedition. The post card includes an image of the 1922 base camp on the Rongbuk glacier that was reused during the 1924 expedition. The post card also includes a "preprinted" note from Noel. There is no evidence that the majority of these cards were ever in Tibet. One exception has been documented in this website. See the combination of the M3b marking and the M4, tractor expedition marking (EV24-M3b-M4_001).

   There are several envelopes that bear an expedition label with the M3b marking that were not mailed (see EV24-M3b_101 through 107). The marking looks accurate except, the word RONGBUK appears damaged. The labels are authentic. I consider the marking to be suspect authenticity.