From: Nigel Tout
Email: nige.tout@vintagecalculators.com
My records show that the Litton Royal Digital III and the Digital IV used General Instrument single chip calculator ICs in late 1971/early 1972. See http://www.vintagecalculators.com/html/royal_digital_iii___iv.html where the Digital III uses a GI 250 date coded 7208, and the Digital IV uses a GI 251 date coded 7206.
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