Ok, here's a dump of some of the info I had on those classes. It'll probably look terrible, but it should suggest certain class inheritance.
IWnd.vftable
---------------------
0 004D0120 >004314D0 Outpost2.?RegisterClassA@IWnd@@EAEPBDXZ
1 004D0124 00431E20 Outpost2.??_EIWnd@@UAEPAXI@Z
2 004D0128 004318A0 Outpost2.?Destroy@IWnd@@UAEXXZ
3 004D012C 004315D0 Outpost2.?CreateEx@IWnd@@UAEHKPBDKHHHHPAUHWND__@@PAUHMENU__@@PAXPAUHINSTANCE__@@@Z
4 004D0130 004316B0 Outpost2.?WndProc@IWnd@@UAEJIIJ@Z
5 004D0134 00431740 Outpost2.?CallFilters@IWnd@@UAEHIIJ@Z
IWnd::IDlgWnd.vftable
---------------------
0 004D0138 >004314D0 Outpost2.?RegisterClassA@IWnd@@EAEPBDXZ
1 004D013C 00431ED0 Outpost2.??_EIDlgWnd@@UAEPAXI@Z
2 004D0140 004318A0 Outpost2.?Destroy@IWnd@@UAEXXZ
3 004D0144 004315D0 Outpost2.?CreateEx@IWnd@@UAEHKPBDKHHHHPAUHWND__@@PAUHMENU__@@PAXPAUHINSTANCE__@@@Z
4 004D0148 004316B0 Outpost2.?WndProc@IWnd@@UAEJIIJ@Z
5 004D014C 00431740 Outpost2.?CallFilters@IWnd@@UAEHIIJ@Z
- - - - - - - - - - -
6 004D0150 00431A80 Outpost2.?DoModal@IDlgWnd@@UAEHPBDPAUHINSTANCE__@@@Z
7 004D0154 00431BF0 Outpost2.?DoModeless@IDlgWnd@@UAEHPBDPAUHINSTANCE__@@PAUHWND__@@@Z
8 004D0158 00431DB0 Outpost2.?DlgProc@IDlgWnd@@UAEHIIJ@Z
IWnd::TFrame.vftable
---------------------
0 004D6158 >004314D0 Outpost2.?RegisterClassA@IWnd@@EAEPBDXZ
1 004D615C 00484120 Outpost2.??_ETFrame@@UAEPAXI@Z
2 004D6160 004318A0 Outpost2.?Destroy@IWnd@@UAEXXZ
3 004D6164 004315D0 Outpost2.?CreateEx@IWnd@@UAEHKPBDKHHHHPAUHWND__@@PAUHMENU__@@PAXPAUHINSTANCE__@@@Z
4 004D6168 004889E0 Outpost2.?WndProc@TFrame@@MAEJIIJ@Z
5 004D616C 00431740 Outpost2.?CallFilters@IWnd@@UAEHIIJ@Z
- - - - - - - - - - -
6 004D6170 00488FC0 Outpost2.?ShutDown@TFrame@@MAEXXZ
7 004D6174 004C14B0 Outpost2.004C14B0
8 004D6178 004C14B0 Outpost2.004C14B0
9 004D617C 004C14B0 Outpost2.004C14B0
A 004D6180 004C14B0 Outpost2.004C14B0
B 004D6184 004C14B0 Outpost2.004C14B0
C 004D6188 00484020 Outpost2.?Activate@TFrame@@UAEXXZ
D 004D618C 00484030 Outpost2.?Deactivate@TFrame@@UAEXXZ
E 004D6190 00484040 Outpost2.?OnIdle@TFrame@@UAEXXZ
F 004D6194 00484050 Outpost2.?PreCreateDlg@TFrame@@UAEXXZ
10 004D6198 00484060 Outpost2.?PostCreateDlg@TFrame@@UAEXXZ
TFrame::Dans_RULE_UIFrame
-------------------------
004D6A08
TFrame::OP2ShellWnd
---------------------
0 130110F8 130092B0 Op2shell.130092B0 ; RegisterClassA
1 130110FC 13007A80 Op2shell.13007A80 ; operator destructor()
2 13011100 1300992E <JMP.&Outpost2.?Destroy@IWnd@@UAEXXZ>
3 13011104 13009928 <JMP.&Outpost2.CreateEx@IWnd@@UAEHKPBDKHHHHPAUHWND__@@PAUHMENU__@@PAXPAUHINSTANCE__@@@Z>
4 13011108 13007F10 Op2shell.13007F10 ; WndProc
5 1301110C 1300991C <JMP.&Outpost2.?CallFilters@IWnd@@UAEHIIJ@Z>
- - - - - - - - - - -
6 13011110 13009350 Entry address ; ShutDown
7 13011114 13009430 Op2shell.13009430 ;
8 13011118 130093C0 Op2shell.130093C0 ;
9 1301111C 13007DB0 Op2shell.13007DB0 ;
A 13011120 13007B70 Entry address ;
B 13011124 13007DC0 Entry address ;
C 13011128 130099A6 <JMP.&Outpost2.?Activate@TFrame@@UAEXXZ>
D 1301112C 130099A0 <JMP.&Outpost2.?Deactivate@TFrame@@UAEXXZ>
E 13011130 1300999A <JMP.&Outpost2.?OnIdle@TFrame@@UAEXXZ>
F 13011134 130093A0 Op2shell.130093A0 ; PreCreateDlg
10 13011138 130093B0 Op2shell.130093B0 ; PostCreateDlg