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| front | back |
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The S4 style was largely identical to the preceding S3 variant. The principal difference was the addition in the S4 design of an alphanumeric packet number printed in the solid-color circle at the upper right of the envelope front:
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| S3 | S4 |
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The reverse of the envelope listed the titles of the three reels in the packet and advertised other View-Master titles in the same general subject category.
A new alphanumeric packet/reel numbering system was instituted beginning with the S4 style. The packet number comprised an alphabetic character (A, B, or C) followed by three digits; reels within a packet were identified with the addition of a fourth digit (1, 2, or 3). For example, packet B656, Moon Rockets and Guided Missiles, consisted of reels B6561, B6562, and B6563.