TRANSISTOR MUSEUM™  Historic Transistor Photo Gallery
Transistor Size  MN27 (1/4” OD X 1/2”)    MN9 (3/16”OD X 3/8”H) Bottom View.  No Packaging.	MOTOROLA MN9 and MN27 TYPE Germanium PNP Alloy Junction USAGE MN9 – RF MN27 - Unknown DATE INTRODUCED Late 1950s CASE STYLES Unpainted Silver Metal (MN9) Black Painted Metal (MN27) AVAILABILITY Rare (Limited Production)
HISTORIC NOTES Several companies involved in early transistor development used proprietary numbering/id systems for their devices.  For example, Raytheon’s first germanium transistors were the “CK” types, including the well known CK722.  Other examples include  the  “ZJ” sequence, used by GE, and the “MN” series used by Motorola.  Likely the “MN” is an abbreviation for “Motorola Number”.  Most transistor companies abandoned the proprietary id system for commercial devices by the late 1960s.  The “MN” sequence used by Motorola was fairly common in the late 1950s, throughout the 1960s, and was in place at the same time that Motorola sold “2N” devices. The two transistors shown above appear to be early pre-production units.  The MN27 has no date code, crude stamping and is not listed in common references of the time.  The unmarked unit (MN9) is an early example (late 1950s) of an RF/high frequency device, developed prior to mesa technology. Neither of these types is shown in price lists or spec sheets.
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