Steven Ritchie was a powerful Oneness apologist. I have continuously benefited from his writings and I am currently archiving his writings on my website. However, in several of his writings, he described Jesus Christ as the "reproduced copy" of the Father's essence of being. See, for example, pages 14-18 of his book The Case for Oneness Theology.
It might be that I have misunderstood Steven Ritchie, but when I read this description of Jesus Christ in his book, I immediately thought, "This sounds like a form of Arianism." It is within the realm of Arianism to believe that Jesus Christ was "created God" or as some Bible translations say, "the only begotten God." More specifically, a "reproduced copy" is basically a clone of the Father's substance as a human being. In this scheme, he who saw Jesus saw the Father, but not the actual Father. He was the replica of the Father, being himself subordinate to the Father.
As a Modalistic Monarchian, I cannot accept that Jesus Christ was a clone of the Father. He was truly the Father himself incarnated as Immanuel God with us as a true human son. For this reason, He is called the Son of God. More precisely, since the incarnation, the Most High God Jehovah (who is the unipersonal Creator of all) has experienced existence in two impersonal natures, being both the Father in heaven (divine spirit with a divine nature) and the Son on earth (divine spirit with a human nature) simultaneously in order to accomplish his eternal purpose. (And just as a side note, this is a concept that Trinitarians should be able to accept because they have the second person in the Trinity doing the exact same things while he exists in two natures simultaneously in heaven and on earth.)
Steven Ritchie believed that the word charakter in Hebrews 1:3 should be interpreted as "reproduced copy" or similarly. However, I believe that if he had considered Hebrews 1:3 as an allusion to Wisdom of Solomon 7:24-26, he would have come up with a different conclusion. Let's compare what we read there with Hebrews 1:3.
Wisdom of Solomon 7:24-26 (RSV): "24 For wisdom is more mobile than any motion; because of her pureness she pervades and penetrates all things. 25 For she is a breath of the power of God, and a pure emanation of the glory of the Almighty; therefore nothing defiled gains entrance into her. 26 For she is a reflection of eternal light, a spotless mirror of the working of God, and an image of his goodness."
Hebrews 1:3 (KJV): "3 Who being the brightness of his glory, and the express image of his person, and upholding all things by the word of his power, when he had by himself purged our sins, sat down on the right hand of the Majesty on high; "
In Wisdom of Solomon, wisdom is personified just as it is in Proverbs 8:22-24, but in these verses we see more clearly that "wisdom" is internalized reason, whereas "the breath" (presumably the logos of Psalm 33:6, but rhema in Hebrews 1:3) is externalized reason. When comparing it with Hebrews 1:3, we have (1) "the breath of the power of God" corresponding to "the word of his power"; (2) the "pure emanation of the glory of the Almighty" corresponding to the "brightness of his glory"; and (3) the "reflection of eternal light," "spotless mirror," and "image of his goodness" corresponding to the "express image." The words "express image" correspond to the Greek word charakter. As with many Greek words, charakter can take on various meanings depending on the context. It is most commonly interpreted as "impress," "marking," or as Steven Ritchie suggested "reproduction." However, I believe that the Greek scholar Henry Alford gave us an important clue in his commentary on Hebrews 1:3 when he cited a usage of charakter as follows: "Lucian, de Amoribus, p. 1061, calls mirrors τῶν ἀντιμόρφων χαρακτήρων ἀγράφους εἰκόνας." The first thing we need to notice is that this citation is is in the context of mirrors. A rough translation of the Greek would be "the counterpart reflection [charakter] — unwritten image." Since this is in the context of a mirror, it fits the context of Wisdom of Solomon 7:26. If we apply this insight to Hebrews 1:3 with the understanding that Hebrews 1:3 is alluding to Wisdom of Solomon 7:24-26, we can see that the Son of God had become the reflection (or as the KJV renders it, "express image") of God the Father's substance. In other words, God the Father was looking in a mirror, as it were, and what he saw was not a "reproduced copy" or "clone," but the reflection of himself, because the Son of God was in fact himself incarnated as a true human son.
I believe this way of understanding charakter in Hebrews 1:3 is better than calling the Son of God a "reproduced copy" or even worse, a "clone." Those words sound Arian. In this regard, I suggest keeping the KJV's translation of charaketer as "express image" with the understanding that this "express" or "exact" image is not another "God person" or a "replica God," but the very reflection of God the Father who manifested himself as the visible image of himself (Colossians 1:15).