Microsoft (which acquired Skype in 2011) has "retired" almost all vintage versions. Even if you find an old .exe installer, the app usually fails to sign in because the modern login servers don't recognize the old protocol.
While Windows 7 itself is no longer supported by Microsoft, the final "modern" version of Skype (version 8) was designed to run on Windows 7 SP1. However, even that support is fading as web standards evolve. How to Get Skype Working Today
If you are still using a Windows 7 machine and need to communicate: Skype Download For Windows 7 5 5
If you are trying to download and use version 5.5 today, you will likely run into several walls:
Search for the latest "Skype for Desktop" installer rather than version 5.5. Microsoft (which acquired Skype in 2011) has "retired"
It sounds like you're looking for information on a very specific, older version of Skype for Windows 7. However, writing a full essay on a software version number is a bit unusual, as most people just want to know if it still works.
Using a version from over a decade ago leaves your system vulnerable. Modern encryption and security patches aren't present in version 5.5. However, even that support is fading as web standards evolve
Are you trying to from that specific version, or do you just need a working video call app for an older computer?