Many 16-bit compilers will produce a file similar to a .COD file, although it may have a different file extension. For example, MicroFocus Cobol can produce a .GRP file, which has the same organization as the .COD file.
The format of this file is that of a mixed listing.
The listing generally contains an input line, identified by line number, followed by the machine instructions generated by the compiler, with the address to the left, the hex instruction in the middle, and an assembler form of the instruction on the right. Some of these files will actually be accepted as is by an assembler, but most compilers document the fact that this is not a supported feature of the compiler.
Obviously, if you know the offset of some instruction, perhaps one that caused a failure, you can use this listing to identify which line of the input program caused the generation of the failing instruction.