Ok Doug, I admit I never used Skype for business but I installed Office 2013 and so here I am to report what I found.
At first I checked on history of Windows update since I remembered something that I installed in the automatic updates but I did not manage to recall it well. So I opened C:\Program files\Microsoft Office\Office15, and found the file Lync.exe. Launching this file it appeared Skype for business as the window title, and in order to be sure of the correct version, I went to "Show menu button", then question mark submenu, about Skype for business, and figured out that yeah it was Skype for business 2015. I hope that it's useful.
-- Inviato da Thunderbird su Windows 10