Altimeter, Model: 4 FGH 10, 20,000 feet, inHg, 3-pointer
80 mm (3 1/8"), 3 pointer, , Range: 0 to 1,000 to 20,000 feet, Inch (Hg) pressure scale, zero at 12 o'clock
3-pointer altimeter for measuring absolute and relative altitudes in the 0 to 20,000 ft range.
Indicating range: 0 to 1000 to 20,000 feet
Gradations: large pointer: 20 ft per line, small pointer: 200 feet per line, third pointer: 5,000 feet per line
Pointer Travel, Long White Pointer: 1,000 ft/rev, Short White Pointer: 10,000 ft/rev, Red-tipped Pointer: 100,000 ft/rev 
Technical Data
Airtight, black plastic housing.  Connection via hose from static pressure sensor to hose connector at the rear.  Kollsman window with Inch scale from 27.6 to 30.5 inches of Hg.  See scale drawing at right for installation dimensions.  Weight: 0.345 kg (12.2 oz).  360° linear scale. 

Note: The W-4325 altimeter is calibrated up to 20,000 feet, but will indicate up to about 26,000 feet (~8,000 m). It will not be damaged if you go higher than that. 

Note: The standard W-4325 altimeter does not accommodate the optional W-4011 scale ring.  However, a specially modified version of the altimeter can be ordered that will work with the scale ring.  The price of the special altimeter is the same as a standard altimeter but the scale ring is extra.  You can select the special version when ordering.  When ordering online the price for the special altimeter includes the W-4011 scale ring.
Manual and Specifications 
Leakage Test 
Adjusting an Offset in the Subscale