HP 1818-2056, 28-pin grey trace cerDIP with gold pins and cavity lid. System of origin unknown.
HP 1818-2251, 28-pin white cerDIP. Function and system of origin are unknown.
HP D1818-2800, B1818-2808, C1818-2813 and A1818-2817, 28-pin perforated grey trace LCCs. These are obvious examples of in-house HP parts, and one of the most unusual chip carriers we've ever seen. Function and system of origin are unknown.
HP C1818-2833. Note that the ceramic substrate is thinner on this chip than on the examples pictured above, and the trace pattern is slightly different. Function and system of origin are unknown.
