Below is a explanation of the Fanuc Alpha part numbers and how they are broke down and what each individual number is.
You can find at the bottom of thr page a part number to match the type of Fanuc encoder fitted to the motor, This will help you if you need to order a replacement encoder.

Fanuc Alpha Motor Model

Models
α1/3000 α2/2000, and α2/3000

A06B-03□□-B△◎◎

□□
71 : Model α1/3000
72 : Model α2/2000
73 : Model α2/3000

△
0 : Taper shaft (standard)
1 : Taper shaft with the brake (2Nm)
5 : Straight shaft
6 : Straight shaft with the brake (2Nm)

◎◎
75 : Pulse coder αA64
77 : Pulse coder αI64
88 : Pulse coder αA1000

The standard shafts used for models α1/3000, α2/2000, and α2/3000 are taper shafts.
Use a taper shaft as far as circumstances, such as the delivery time and maintenance permit.

Models
α3/3000 α6/2000 and α6/3000

A06B-01□□-B△◎◎

□□
23 : Model α3/3000
27 : Model α6/2000
28 : Model α6/3000

△
0 : Taper shaft (standard)
1 : Taper shaft with the brake (8Nm)
5 : Straight shaft
6 : Straight shaft with the brake (8Nm)

◎◎
75 : Pulse coder αA64
77 : Pulse coder αI64
88 : Pulse coder αA1000

The standard shafts used for models α3/3000, α6/2000, and α6/3000 aretaper shafts.
Use a taper shaft as far as circumstances, such as the delivery time and maintenance permit.

Models
α 12/2000, α12/3000, α22/1500, α22/2000,
α22/3000, α30/1200,α30/2000, α30/3000,
α40/2000, and α40/2000 (with fan)

A06B-01□□-B△◎◎

□□
42 : Model α12/2000
43 : Model α12/3000
46 : Model α22/1500
47 : Model α22/2000
48 : Model α22/3000
51 : Model α30/1200
52 : Model α30/2000
53 : Model α30/3000
57 : Model α40/2000
58 : Model α40/2000 (with fan)

△
0 : Straight shaft (standard)
1 : Straight shaft with the brake (35Nm)
5 : Taper shaft
6 : Taper shaft with the brake (35Nm)

◎◎
75 : Pulse coder αA64
77 : Pulse coder αI64
88 : Pulse coder αA1000

A straight shaft is fitted as the standard shaft for models α12 to α40.
When early delivery and case–of–maintenance are important, a straight
shaft should be used. For model α40, a tapered shaft is not available.

Models

α65/2000, α100/2000 and α150/2000

A06B-03□□-B△◎◎

□□
31 : Model α65/2000
32 : Model α100/2000
33 ; Model α150/2000

△
0 : Taper shaft (standard)
2 : Taper shaft with the brake (100Nm)

◎◎
75 ; Pulse coder αA64
77 : Pulse coder αI64
88 : Pulse coder αA1000

Models
α300/2000, α400/2000

A06B-013□-B0◎◎

□
7 : Model α300/2000
8 : Model α400/2000

◎◎
75 ; With the pulse coder αA64
77 : With the pulse coder αI64
88 : With the pulse coder αA1000

For these models, a tapered shaft is standard. a straight shaft is not available.
For these models the brake option is not available.

Pulse Coder Part numbers
αA64 A860-0360-T101, A860-0360-V501 and A860-0360-T201
αI64  A860-0365-T101, A860-0365-T101
αA1000 A860-0370-T201, A860-0370-V501

Fanuc Alpha I Motors

A06B-□□□□-B△○▽#◎◎◎◎
□□□□
An ordering specification number are described on the tables below.
* Every combination doesn’t exist.
△
0 : Taper shaft
1 : Straight shaft
2 : Straight shaft with a key groove
3 : Taper shaft with a 24VDC brake
4 : Straight shaft with a 24VDC brake
5 : Straight shaft with a key way and a 24VDC brake
* Do not select “Straight shaft with a key groove” when a large torque or abrupt acceleration rate
is required.
○
0 : Standard
1 : With a fan
2 : With a high-torque brake
3 : With a high-torque brake and a fan
4 : With a strong fan
5 : With a fan
* When “With a high-torque brake” is selected (○ = 2 or 3), specify△ = 3 to 5.
▽
0 : Pulsecoder αiA 1000
1 : Pulsecoder αiI 1000
2 : Pulsecoder αiA 16000
◎◎◎◎
0000 : Standard
0100 : IP67 specification

Pulse Coder part numbers
αiA 1000 A860-2000-T301
αiI 1000 A860-2005-T301
αiA 16000 A860-2001-T301