What precisely does the term 'Proto-Adamantium' refer to?

Question

'Proto-Adamantium' is a term used in association with the metal Captain America's shield is composed of in the Marvel Earth-616 comics.

That metal was originally a fusion of Wakandan Vibranium and an experimental steel alloy created by the American metallurgist, Dr. Myron MacLain. It still has both of those things in it, but it now has some Asgardian Uru in it too, as a result of the shield being shattered by Odin's brother, Cul Borson, and then repaired by Asgardian dwarves in the Fear Itself storyline. The Uru component isn't relevant to the question, though, since the term 'Proto-Adamantium' has been around since the 1980s, long before that storyline.

So then, does the term 'Proto-Adamantium' refer to the metal which was created by the fusion of Wakandan Vibranium and MacLain's experimental steel alloy? Or does it refer to the experimental steel alloy on its own?

Answer 1

The term 'Proto-Adamantium' refers to MacLain's experimental steel alloy on its own.

The term isn't used much, if at all, in the actual comics. However, the Official Handbook of the Marvel Universe makes it clear that Proto-Adamantium is the experimental steel alloy which was fused with Wakandan Vibranium, rather than the metal that was created as a result of that fusion.

MacLain began experimenting with the process that creates adamantium as a young scientist in the employ of the United States government in the early 1940s. By accident he created a special adamantium compound which is more nearly indestructible than any form of adamantium created ever since, and then through another accident, fused this adamantium sample he had created with a sample of an unknown metal which is now known to have been Wakandan Vibranium (see Vibranium). The result was the large rounded specimen of alloy which is the most virtually indestructible substance known to man. This alloy specimen was given to Captain America to serve as his shield (see Captain America, Captain America's Shield). The exact chemical composition of Captain America's shield and the exact degree to which it is indestructible have never been determined, nor has MacLain or anyone else ever learned how to duplicate either the special adamantium compound used in the creation of the shield, which is known as Proto-Adamantium, or the process which fused the Proto-Adamantium with the Wakandan Vibranium.

_{Official Handbook of the Marvel Universe Vol. 1 #15 (May, 1984)}