different interop references twin opposite computers doesn't work

when i supplement anxiety microsoft.office.interop.excel computer, visible studio adds digest file:

<comreference include="excel">
  <guid>{00020813-0000-0000-c000-000000000046}</guid>
  <versionmajor>1</versionmajor>
  <versionminor>5</versionminor>
  <lcid>0</lcid>
  <wrappertool>primary</wrappertool>
  <isolated>false</isolated>
</comreference>

there another developer organisation gets errors needs supplement dll record digest called interop.excel.dll, replaces formula above digest file:

<reference include="interop.excel, version=1.5.0.0, culture=neutral, processorarchitecture=msil">
  <specificversion>false</specificversion>
  <hintpath>my project\interop.excel.dll</hintpath>
</reference>

this does work computer.

could greatfully explain differences between twin methods, best, initial operative computers?