All IBM equipment is assigned a four digit value. This is known as the 'system type'. There is sparse information cataloguing all of the system types: this page attempts to rectify that by documenting as many as possible.
This is an ongoing project (probably will never be completed).
Categories of 'similar' types will be grouped together on the same rows: these similar types will share some core similarities with one another, but vary in form factor for instance.
PC 300
IBM 300PL
Type: 6862, 6872, 6890, 6892
Type: 6584, 6594, 6595
Type: 6565, 6566
Type: 6562, 6592
IBM 300GL
Type: 6268, 6278, 6288
Type: 6338
Type: 6267, 6277, 6287
Type: 6561, 6591
Type: 6563, 6564, 6574, 6593
PC300:
Type: 6577
PC350:
Type: 6587
NetVista
A Series
A10
Type: 2169
A20
Type: 6269
A20i
Type: 6276
A21
Types: 6342(!), 6337
A21i
Types: 2256, 2257(?), 2254(?)
A22
Types: 2257, 6029, 6341(!), 6339(!)
A22p
Type: 6049
A30
Type: 8315
A30p
Type: 8310
A40
Types: 6058, 6568, 6578, 6648
A40i
Types: 2284, 2251(?)
A40p
Types: 6059, 6569, 6579, 6649
A60
Type: 6833
A60i
Type: 6832
M Series
M41
Type: 6790
M42
Type: 8305
S Series
S40
Type: 6644, 6645
S40p
Type: 6646
S42
Type: 8319
X Series
X40
Types: 6643
X40i
Types: 2179
X41
Types: 2283
N Series
N2200e/w/l Thin Client Express
Type: 8363
N2800e/w/l Thin Client Express
Type: 8364
Aptiva
M Series
A Series
C Series
L Series
S Series
Types: 2159
E Series
Types: 2171, 2158
ThinkCentre (pre-lenovo)
M Series
ThinkCentre M50
Type: 8128, 8185, 8186, 8187, 8188, 8189, 8190, 8413, 8414, 8415, 8430, 8431
ThinkCentre M51
Type: 8104, 8106, 8108, 8118, 8120
ThinkCentre M52
Type: 8113, 8114, 8212, 8099, 8116, 8215, 9210, 9211
S Series
ThinkCentre S50
Type: 8086, 8087, 8088, 8094
ThinkCentre S51
Type: 8098, 8171, 8172, 8173
A Series
ThinkCentre A30
Type: 2296, 8191, 8198, 8199, 8316, 8434
ThinkCentre A50
Type: 8089, 8090
ThinkCentre A50p
Type: 8192, 8193, 8194, 8195, 8196, 8197, 8432, 8433
ThinkCentre A51
Type: 8105, 8107, 8424, 8425
ThinkCentre A52
Type: 8155, 8156, 8157, 8158, 8159, 8160
ThinkPad (pre-lenovo)
T40/41/42
Types: 2373, 2374, 2375, 2376, 2378, 2379, 2668, 2669, 2678, 2679, 2686, 2687
T43
Types: 1871, 1872, 1873, 1874, 1875, 1876, 2668, 2669, 2678, 2679, 2686, 2687
T60
Types: 1951, 1952, 1953, 1954, 1955, 1956, 2007, 2008, 2009, 2613, 2623, 2637
701C
Type: 2630
800
Type: 6020
820
Type: 6040
821/822/823
Type: 7247
850
Type: 6042
851/860
Type: 7249
WorkPad Z50
Type: 2608
Transnote
Type: 2675
X41
Type: 2525
Monitors
IBM High-Tier/Professional Series
T220/T221
Type: 9503
T120
Type: ????
T119
Type: ????
T117
Type: ????
T115
Type: ????
T560
Type: 6656
T541H/L150p
Type: ????
ThinkVision (pre-lenovo)
L200p
Type: 6736
L191p
Type: ????
L171p
Type: ????
L170p
Type: ????
Misc.
P260/P275
Type: ????
C220p
Type: ????
PS/2 Displays
Types: 8503, 8504, 8506, 8507, 8508, 8512, 8513, 8514, 8515, 8516, 8518
Industrial Displays
Types: 5532, 7534, 7544, 7554
IntelliStation
A Pro
Type: 6224
Type: 6217
E Pro
Type: 6893
Type: 6867
Types: 6836, 6846
Types: 6204, 6214
Types: 6216, 6226
M Pro
Type: 6868
Type: 6888
Type: 6898
Type: 6889
Type: 6849
Type: 6850
Type: 6231
Type: 6233
Type: 6229
Type: 6219
Types: 6220, 6230
Type: 6225 (Tall Pentium 4 with lots of I/O)
Type: 6218 (Tall Pentium D with lots of I/O)
Type: 9229 (Core2Duo Tarako
Type: 9237 (Compact Japanese unit)
R Pro
Type: 8654
Type: 6851
Z Pro
Type: 6899
Type: 6865
Type: 6866
Type: 6894
Type: 6221
Type: 6223
Type: 9228 (Final Z Pro, fastest of the bunch)
POWER 185
Type: 7047-185
POWER 265
Type: 9112-265
POWER 275
Type: 9114-275
POWER 285
Type: 9111-285
System x (pre-lenovo)
BladeCenter HS22
Type: 1911, 1936, 7809, 7870
BladeCenter HS22V
Type: 1949, 7871
BladeCenter HS23
Type: 1929, 7875
BladeCenter HS23E
Type: 8038, 8039
BladeCenter HX5
Type: 1909, 1910, 7872, 7873
Flex System x220 Compute Node
Type: 2585, 7906
Flex System x222 Compute Node
Type: 7916
Flex System x240 Compute Node
Type: 7863, 8737, 8738, 8956
Flex System x440 Compute Node
Type: 2584, 7917
iDataPlex dx360 M2
Type: 7321, 7323
iDataPlex dx360 M3
Type: 6391
iDataPlex dx360 M4
Type: 7912, 7913, 7918, 7919
IBM NeXtScale Node
Type: 5455
Smart Analytics System
Type: 7949
System x3200 M2
Type: 4367, 4368
System x3200 M3
Type: 7327, 7328
System x3250 M2
Type: 4190, 4191, 4194, 7657
System x3250 M3
Type: 4251, 4252, 4261
System x3250 M4
Type: 2583
System x3250 M5
Type: 5458
System x3300 M4
Type: 7382
System x3400 M2
Type: 7836, 7837
System x3400 M3
Type: 7378, 7379
System x3500 M2
Type: 7839
System x3500 M3
Type: 7380
System x3500 M4
Type: 7383
System x3530 M4
Type: 7160
System x3550 M2
Type: 4198, 7946
System x3550 M3
Type: 4254, 7944
System x3550 M4
Type: 7383, 7914
System x3620 M3
Type: 7376
System x3630 M3
Type: 7377
System x3630 M4
Type: 7518, 7519
System x3650 M2
Type: 4199, 7947
System x3650 M3
Type: 4255, 5454, 7945
System x3650 M4
Type: 7915
System x3650 M4 BD
Type: 5466
System x3650 M4 HD
Type: 5460
System x3690 X5
Type: 7147, 7148, 7149, 7192
System x3750 M4
Type: 8722, 8733, 8718, 8752
System x3755 M3
Type: 7164
System x3850 X5
Type: 7143, 7145, 7146, 7191
System x3850 X6/x3950 X6
Type: 3837, 3839
System x3950 X5
Type: 7143, 7145, 7146, 7191
Personal System/2
Academic System
Type: 6152
PS/2 Model 25
Types: 8525-001, 8525-004
PS/2 Model 30
Type: 8530
PS/2 Model 35
Type: 8535
PS/2 Model 40
Type: 8540
IBM L40SX Portable
Type: 8543
PS/2 Model 50
Type: 8550
PS/2 Model 53
Type: 8553
PS/2 Model 55
Type: 8555
PS/2 Model 56
Type: 8556
PS/2 Model 57
Type: 8557
PS/2 Model 60
Type: 8560
PS/2 Model 65
Type: 8565
PS/2 Model 70
Type: 8570
IBM P70 Portable
Type: 8573-121
IBM P70 Portable 'custom order black casing'
Type: 7186
IBM P75 Portable
Type: 8573-401
IBM ???? Portable
Type: 8575
PS/2 Model 76
Type: 8576
PS/2 Model 80
Type: 8580
PS/2 Model 85
Type: 9585
PS/2 Model 90
Type: 9590, 8590 (older model)
PS/2 Model 95
Type: 9595, 8595 (older model)
PS/2E 'Model 33'
Type: 9533
Personal System/1
PS/1 Consultant
Type: 2155
PC Server
PC Server 300
Type: 8640
PC Server 310
Type: 8639
PC Server 320
Type: 8640
PC Server 500 / 520
Type: 8641
PC Server 700
Type: 8642
Industrial Systems
Type: 7531, 7532, 7537, 7546, 7537, 7546, 7541, 7542, 7552, 7561, 7562, 7568
RS/6000
39H
Type: 7012
58H / J40
Type: 7013
3BT
Type: 7030
40P:
Type: 7020
43P Model 150
7043-150
43P Model 260
7043-260
44P Model 270
7044-270
Misc.
SCSI Multi-Storage Enclosure
Type: 3517
Enterprise Expansion Enclosure
Type: 3518
C-Series Optical Library (34L2578)
Type: 3995
PS/2 Printers
Types: 2205, 2380, 2390, 2381, 2391, 4019, 4028, 4029, 4072, 4201, 4202, 4207, 4208, 4212, 4226, 5201, 5202, 5204
External 8" Floppy Disk Drive
Type: 9331-011
External Tape Drive
Type: 8767-HHX
Mainframe Modem
Type: 3865-02
External Modem
Type: 7855-10
Cordless Computer Connection
Type: 7852-41
External CD-ROM Drive
Type: 1969-011
Dual Token Ring CAU
Type: 8230-013