These postcard-sized advertising cards feature reprints of the Dinosaur Series trading cards issued by Nu-Card Sales in 1961 but differ in that (1) this set only includes 36 cards; the first 35 of which have the same images as the first 35 of the Dinosaur Series set which contained 80 cards, (2)  these cards are three-times larger than the trading cards, (3) these cards are entirely black & white as opposed to the trading cards which have aquamarine-like highlights and borders, (4)  these cards have descriptive captions ranging from dramatic to silly unlike the trading cards which only include the animal's identification, and (5) the 36th card, which shows "A Simplified Family Tree of Dinosaurs", was not included in the trading card set.  Collector/researcher extraordinaire, Jeff Quinn, has identified what appears to be the source of this image, a publication from the American Museum of Natural History called “Dinosaurs” by Edwin H. Colbert, Publication No. 70, 1960 (Images of the book cover and family tree illustration are provided below).  The family tree was drawn by John C. Germann although the acknowledgement in the bottom-left corner of the book illustration is missing from the card.

 

Based on the images provided by Jeff Quinn, the cards were apparently issued in clear cellophane packages containing two cards each (see images below).  The method of distribution is uncertain though its been theorized that a pack of cards might have been handed out to customers purchasing toy models at the Hobby Trading Post itself or perhaps at other hobby stores that carried Hobby Trading Post-sponsored models.

 

The backs of the cards advertise various hobby kits. From what I've seen, each kit was advertised on three different cards (see checklist below).

Kits shown on the backs of the cards: Kit 119 = F8U-1 Crusader, Kit 210 = Black Falcon, Kit 374 = P B Y "Catalina", Kit 378 = Regulus II with Operating Launcing Platform, Kit 382 = TWA Boeing 707, Kit 504 = Piasecki H-21 "Work Horse", Kit 598 = U.S. Navy Task Force, Kit 708 = Atomic Submarine S.S.N. Nautilus, Kit 1602 = Twin Signal Set, Kit 1604 = Crystal Radio Kit, Kit 1611 = Fixed Crystal Radio Kit, Kit 1617 = 1 Tube Radio Kit