If you need to determine your WAC Server build, it is relatively easy.
In Internet Explorer (in this example IE11), browse to the location where documents are stored.
Hit F12 key (make sure the "F lock" key is selected). You will then see the below window.
1. Choose the "Network (Ctrl + 4)" icon.
2. Click the Play button "Enable network traffic capturing (F5)"
3. Click "Details"
4. Click "Response headers"
5. You will see the WAC build next to "MicrosoftSharePointTeamServices".