I acquired my first Munter 74 eight from Eiselin Sport in 1982, and my second on eBay from John J. Rapa in 2022.
The Munter Egg Mark 3 is forged from aluminum alloy. Mine is 181 mm. tall, 124 mm. wide, and 10 mm. thick. The rope hole is 73 mm. high and 101 mm. wide. The top center thickness is 10 mm. The shaft length and width are 39 mm. and 66 mm., respectively. The auxiliary hole is 17 mm. high and 17 mm. wide. The eye measures 49 mm. by 28 mm. The ears are 8.3 mm. long. My Munter Egg Mark 3 weighs 219 g.
One side of my Munter Egg Mark 3 has "MUNTER" and "+pat+" in raised forged letters.
The Munter Egg Mark 3 falls into my miscellaneous figure eights with ears category. Werner Munter developed this eight, and received Swiss Patent #530212 for the design. The device closely matches the "Munter Egg Mark 3" shown in Norman Kingsley's book, but not exactly. I've always assumed that that drawing is not to scale, and actually depicts this device. It does not match the two versions shown in Figures 1 and 2 of the patent, so calling it "Mark 3" is apparently credible.
Kingsley wrote, "MOUNTAIN writes that older, simpler models were accompanied by a twelve page manual, and wonders if new improved complex ones have a 24-pager to instruct users." When I bought my first one in 1982, there was no accompanying documentation from the manufacturer, but I did get an instruction sheet from the retail store. My second one, acquired in 2022, came with an original 24-page instruction manual, answering the question in the affirmative.
I'll start with the good point: the ears don't get in the way. The instructions show three arrangements for rappelling. The first uses a carabiner as a brake bar, the second is set up like an Edelrid Bankl Plate, and the third is the traditional figure eight arrangement. It also shows several arrangements for belaying. The Munter Egg is larger than this kind of rappel or belay device needs to be and offers no particular advantages that I can see, so I never use mine.
 Norman Kingsley, 1975. "Icecraft." La Siesta Press, Glendale CA, p. 105.