In this analysis of a Portable Executable linked using Microsoft Linker (6.0), down in the Imported Objects section, the website makes some very specific claims:
3 .OBJ Files (COFF) linked with LINK.EXE 5.12 (Visual Studio 5 SP2) (build: 9049) 4 .OBJ Files (COFF) linked with LINK.EXE 6.00 (Visual Studio 6) (build: 8168) 178 .C Files compiled with CL.EXE 12.00 (Visual Studio 6) (build: 8168) 26 .CPP Files compiled with CL.EXE 12.00 (Visual Studio 6) (build: 8168) 41 .ASM Files assembled with MASM 6.13 (Visual Studio 6 SP1) (build: 7299) 12 .OBJ Files linked with ALIASOBJ.EXE 6.00 (Internal OLDNAMES.LIB Tool) (build: 7291)
As far as I know, all debug information is stripped from the executable, and there certainly aren't 178 embedded ascii strings ending in ".C".
The sections in the PE are the usual .text, .rdata, .data, .rsrc.
What type of additional information or metadata in the EXE could be used to make guesses about the original object files?