This mold was copied from a sculpture by Don Manning for Nosco Plastics. Originally shown in an insert of a Breyer Dealer catalog in 1961. They were also shown in the 1962 Montgomery Ward Holiday Catalog. 8.5"H x 5"L. Metallic Gold with Black shaded eyes.
For an excellent history lesson on these models, and creator Don Manning, check out Kirsten Wellman's blog post: http://modelhorsecollectibility.blogspot.com/2018/03/.