Introduced about 1972, using calibre 550. Available in stainless steel or gold plated. Advertised in 1973 as the “Ricoh quartz crystal wrist computer, guaranteed accurate to 5 seconds a month ... miniature miracle ... guaranteed for two years” for $295 (the mechanical watches carried a ten year guarantee)
The 550002 features better accuracy than the 550003 (+-5 secs/month vs +-15 secs/month) despite using the same movement. There is a difference in cost reflecting this (¥93,000 vs ¥55,000)
Cases†
- Stainless steel - 93,000円
- Gold plated - 118,000円 - $295 in 1973
Dials†
- White stone at 12, possibly a quartz
- Day & date apertures at 6
- Tiger eye
- Painted
Example serial numbers - Case - Movement†
- 122376 - Stainless steel
- 122646 - Stainless steel
- 122797 - 022966 - Stainless steel - Dated Sep 1972, also marked B54AB
- 123148 - Stainless steel
- 123509 - Stainless steel
- 123605 - 015227 - Stainless steel, dated Jul 1972
- 123??? - Stainless steel, dated Jul 1972
- 312603 - 024188 - Stainless steel, dated Sep 1972, marked “550002 CA”, YouTube video https://youtu.be/ng4ypGF0oOs
- 312928 - Stainless steel - Marked "550002 CA", two tone silvered dial
- 313224 - Stainless steel - Marked “550002 CA”, plain silvered dial
- 313709 - 024887 - Stainless steel - Marked “550002 CA”, two tone silvered dial
- 322389 - 015145 - Gold plated - Dated Aug 1972
- 323264 - 021906 - Gold plated, marked “550002 CA”, brown fade dial, gilt mesh bracelet
- 422372 - Stainless steel - Tiger eye dial signed "Tiger eye", 93,000 yen tag
- 622112 - Stainless steel - Marked “550002 BA” - Dated Z-72 for Dec 1972, case only, serial number faint so not 100%
- 622272 - Stainless steel - Marked “550002 BA”
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