The following resources can be used as references:
Office File Formats (Not including OOXML formats)
Office Open XML File Formats (ECMA-376, ISO/IEC 29500)
If you don’t have MS Office installed, you can try their online service to see the attached file to see what it should be looks like.
Steps to use:
1. Open a bug report from here.
2. Right click an attachment link, then select “Copy link adress”. Note: the attached file must be MS Office format, and not “Details” link at its right side.
3. Open http://www.officewebviewer.com
4. Paste the URL into input box, then click Create URL.
5. Click “preview in a new window”.
From here we can see how does Microsoft did in their Office suite.