Comment on June 2017 CU for SharePoint 2013 product family is available for download by Stefan Goßner

Hi Tom,
it is impossible to install June 2017 updates without SP1.
So if June 2017 update was installed, then SP1 is installed on your servers as well.
Without SP1 your server would be unsupported since more than two years and you would also not have been able to install any security fixes since April 2015.
Cheers,
Stefan