    New chain ID            Original chain ID

6tcl-pdb-bundle1.pdb:
           A                        A1
           B                        B1
           C                        C1
           D                        D1
           E                        E1
           F                        F1
           G                        I1
           H                        J1
           I                        K1
           J                        L1
           K                        M1
           L                        X1
           M                        A2
           N                        B2
           O                        C2
           P                        D2
           Q                        E2
           R                        F2
           S                        I2
           T                        J2
           U                        K2
           V                        L2
           W                        M2
           X                        X2

6tcl-pdb-bundle2.pdb:
           A                         A
           B                         B
           C                         C
           D                         D
           E                         E
           F                         F
           G                         I
           H                         J
           I                         K
           J                         L
           K                         M
           L                         X
           M                        AA
           N                        BB
           O                        CC
           P                        DD
           Q                        EE
           R                        FF
           S                        II
           T                        JJ
           U                        KK
           V                        LL
           W                        MM
           X                        XX
