The Manster (1959)

Here’s a model capturing the essence of The Manster. A scientist transplanted some tissues onto the neck of a victim, and with the help of hormones, the tissues grew into another head.

Kit Maker: Resin From the Grave

From Wikipedia:

The Manster is a 1959[1] tokusatsu horror film, a coproduction between the US and Japan, starring Peter Dyneley. The film was notable for its creative use of special effects.

The film is also known as Doktor Satan in Greece, The Split and The Two-Headed Monster.