http://blog.youkuaiyun.com/mickeyfirst/archive/2008/11/07/3247597.aspx
The following table summarises the UID usage for the common system-defined polymorphic DLLs:
Description | Usual extension | UID2 | UID3 required? | application | app | KUidApp in apadef.h | yes | animation | ani | KWservAnimDllUid in w32adll.h | no | control panel applet | ctl | KUidSystemControlDll in apgctl.h | yes | ECom plug-in | ECOMIIC | 0x10009D8D | yes | front-end processor | fep | 0x10005e32 | yes | MIME recognizer | mdl | 0x10003A19 | yes | serial protocol module | csy | KUidUnicodeCommServerModuleV02 in cs_port.h | no | socket server protocol module | prt | KUidProtocolModule in es_prot.h | yes | Server-side MTM | dll | KUidMtmServerComponent in msvruids.h | yes | Client-side MTM | dll | KUidMtmClientComponent in msvruids.h | yes | UI MTM | dll | KUidMtmUiComponent in msvruids.h | yes | UI Data MTM | dll | KUidMtmUiDataComponent in msvruids.h | yes | |