The archive exists — now check the restore

Unpacking without errors does not mean the copy matches the archive. tar can compare them itself.

tar -df compares every archive member with the file on disk, relative to the -C directory: contents, mode, owner and modification time. If everything matches, it prints nothing. Here is the comparison for a copy someone edited by hand:

$ tar -df app-full.tar -C restore
tar: app/.release: Warning: Cannot stat: No such file or directory
app/bin/report.sh: Mode differs
app/config/app.conf: Mod time differs
app/config/app.conf: Size differs

Cannot stat means the file is missing, Mode differs means the mode changed, and Size differs with Mod time differs mean the contents changed. Extra files that are not in the archive go unnoticed by tar -df: you see them in ls -laR.