Second class vehicles are in 2xx series and composite vehicles in 3xx series.
It can be assumed that DT 304 would have been Class 116 TCs, which were then downgraded to 2nd class only becoming DT 215.
DT 201
Class 101
TS
Diagram BR 622
DT 202
Class 101, 111
TS
Diagram BR 623
DT 203
Class 104
TS
Diagram BR 583
DT 204
Class 107
TS
Diagram BR 647
DT 205
Class 108
TS
Diagram BR 547
DT 206
Class 108
TS
Diagram BR 545
DT 207
Class 110
TS
Diagram BR 648
DT 208
Class 115, 127
TS
Diagram BR 590
DT 209
Class 116
TS
Diagram BR 856B
DT 210
Class 120
TS
Diagram BR 572
DT 211
Class 123
TS
Diagram BR 568
DT 212
Class 124
TS
Diagram BR 573
DT 214
Class 127
TS
Diagram BR 589
DT 215
Class 116
TS
Diagram BR 555
DT 216
Class 119
TS
Diagram BR 542
DT 217
Class 120
TS
Diagram BR 561
DT 218
Class 104
TS
Diagram BR 582
DT 219
Class 116
TS
Diagram BR 855B
DT 220
Class 101
TS
Diagram BR 624
DT 221
Class 111
TS
Diagram BR 625
DT 223
Class 126
TS
Diagram BR 571
DT 224
Class 126
TS
Diagram BR 857
DT 225
Class 101
TS
Diagram BR 668
DT 226
Class 127
TS
Diagram BR 589
DT 227
Class 115
TS
Diagram BR 599
DT 228
Class 101
TS
Diagrams BR 622,
BR 623 &
BR 624
DT 229
Class 115, 127
TS
Diagram BR 590
DT 301
Class 101
TC
Diagram BR 624
DT 302
Class 104
TC
Diagram BR 582
DT 303
Class 115
TC
Diagram BR 599
DT 305
Class 117, 118
TC
Diagram BR 851
DT 306
Class 123
TC
Diagram BR 567
DT 307
Class 115
TC
Diagram BR 599