This is DC’s first Atom, Al Pratt, who was introduced in All-American Comics 19 back in 1940. The Atom was also featured in Flash Comics and was a member of the Justice Society of America appearing in All Star Comics.

Basic Figure: Aurora Superboy
Hands: Revell Phantom
Head: I removed the hair and ears and puttied the face. To get a really smooth surface for the mask, I vacuum formed sheet styrene over the reworked head using a Mattel Vac-U-Form machine.
Torso: Trunks, belt, back and chest were sanded and blended together with AMT model car putty, then vac formed to create the new high trunks.
Belts: Jo-Han model car hood straps
Cuffs: Styrene rod
Paints: Ulrich 410-M Styrene

Completed in 1967.

I actually built two of these models and gave the second one to a friend.