Despite it's gimmicky nature, I picked one up a while back.
Apologies for the horrible scan (my scanner really hates these bloated card holders/cases).
As you can see I picked up a 1/1 Blank Back of Hiroki Kuroda. More specifically Kuroda's card in 2014 Opening Day.
I had been wanting to add a 1/1 Big Hirok card to my collection for a while now but the ones that popped up were always more expensive than what I was willing to pay.
I managed to pick up this blank back for a little less than $15 (including shipping fees), which is pretty fair IMO. Now I can proudly proclaim that I have a 1/1 card of all three of my main PC guys (Hirok, Betances & Jagielo).
Now that I have this 1/1 I'm tempted to try and go after the complete rainbow for Hirok's Opening Day cards. I already received the base from Nick and it shouldn't be too hard to find the blue parallel. Although the printing plates and purple Toys R Us parallel (yes, toys r us has their own Opening Day parallels too) will be something else.
On second thought forget it, I'm too lazy/cheap to undergo such a thing.
Anyway, thanks for stopping by and tolerating my horrible scans. As always, take care :).