Part Number Ordering Information, example and explanation:

RNC55J1001FS where,

RNC
55
J
1001
F
S
Style and Termination Type (Fixed, Film, Established Reliability Resistors Conforming to MIL-R-55182)
Shape, Dimensions, Power Rating of the Resistor
Characteristic
Resistance Value (Ohms) 
Note: RNC90Y resistance values are expressed by six characters
Resistance Tolerance
Failure Rate Level

Part number ordering options are developed using the following criteria:

Style
Detail Specification
  
Terminal Type
RN^50
MIL-PRF-55182/7
  
C = Solderable/Weldable 
(Type C31, C32, or C52 of MIL-STD-1276)
RN^55
MIL-PRF-55182/1
  
N = Weldable 
(Type N22 of MIL-STD-1276)
RN^60
MIL-PRF-55182/3
  
R = Solderable
RN^65
MIL-PRF-55182/5
    
RN^70
MIL-PRF-55182/6
    
RNC90Y
MIL-PRF-55182/9
    
Hermetically
Sealed
Nonhermetically
Sealed
Resistance Temperature Characteristic
(Referenced to +25°C)
C
H
±50 parts per million/°C
E
J
±25 parts per million/°C
 
K
±100 parts per million/°C
 
Y
(RNC90 style only)
±5 parts per million/°C up to +125°C
±10 parts per million/°C from +125°C to +175°C
Resistance Tolerance
  
Failure Rate Level
V = ± 0.005%
  
P = 0.1%/1000 hrs (Level 2)
T = ± 0.01%
  
R = 0.01%/1000 hrs (Level 2)
A = ± 0.05%
  
S = 0.001%/1000 hrs (Level 1)
B = ± 0.1%
  
T = Space Level (See Application Notes)
D = ± 0.5%
    
F = ± 1.0%
    
Resistance Values:
For all styles except RNC90Y resistance values in ohms are identified by four characters. The first three digits represent significant figures and the last digit specifies the number of zeroes to follow. For example 1001 indicates 1,000 ohms and 1002 indicates 10,000 ohms. For values less than or equal to 100 ohms the letter "R" is used to indicate a decimal point. For example 10R0 indicates 10.0 ohms.

RNC90Y resistance values in ohms are identified by six characters consisting of five digits and a letter. The letter is used simultaneously as a decimal point and as a multiplier. For resistance values:

a. Greater than or equal to 1 ohm but less than 1,000 ohms, the letter "R" is used to represent a decimal point.
b. Greater than or equal to 1,000 ohms but less than 1 megohm, the letter "K" is used to represent a decimal point.

Also, it is possible to order RNC90Y resistors with tolerance V, T, A, or B with any resistance value within the minimum and maximum values shown in the tables herein. However, it is preferred that values be chosen from the standard values shown in the tables.