I have a Discover It card which gives me my Transunion score each month. You can also sign up with them to get your Experian score without even having one of their cards. But I've never known what my true Equifax score was because the only place I've seen one was on Credit Karma which is a Vanguard score.
I just tried the pre-qual Discover site even though I figured that it wouldn't work because I haven't had my current card for a year yet. I'm hoping to get another Discover It card once my first year of cash back match is done.
The pre-qual site said that I had no current offers because of the age of my most recent Discover card. It had the standard wording that you could obtain a free copy of your credit report by writing in, and I noticed that it was the Equifax address instead of Experian. Then it said that they had also obtained my credit score from them and showed the number, again stating that they had obtained this information from Equifax.
I'm pretty sure they pulled Transunion when I originally got the card. Maybe it was just luck of the draw that I got Equifax today, but I was pretty happy to know all 3 of my scores for free from Discover. 
Credit Karma Vanguard score was a 780, and the Fico 8 score that I just saw was a 741.
