Blank! We all know what it is, unless you have a tendency to leave other envelopes in the bathroom..

I like to recycle them to, but I'm a little bit dorky like that!

Blank is the best...

In my opinion and like Carly said I like to recycle my envelopes as well helps the environment

Baby, you can put "Obama's Biaatch" on that thing, and it won't matter much lol.

As long as the benjies are accurate, we don't much care ha ha. I don't exactly keep them.

First off they end up in the trash...  as mucgh a give away as condom wrappers.  Think cops don't know?  
Second envolupes are ok in a suit but not casual clothes.  
I make sure the donation is correct, fold in half & secure with a Paper Clip.  This goes in my key pocket (varies with my clothing).  On a first date, I place it on the dresser or the vanity...  either way I leave the room briefly.  
On repeat dates, she customarily places a chair by her dresser to recieve my clothes.  I am in the habbit of emptying my pockets...  much easier to dress that way & less likely to lose an object which I did with a civie GF back in the dark ages.  The first thing on the dresser is the donation & my pocket junk surrounds it.  (I've never missed the donation, one of my fears, but if so I'd find it as I refilled my pockets.)  So I refill my pockets, leaving the donation on the dresser.  I don't look at it directly again.  Sometimes in the back & forth of dressing & bathroom for us both the donation may disappear...  sometimes, it's still there when I say my goodbyes...  but this is old school & it avoids shattering the illusion.  
The only time this hasn't worked smoothly, my clothes were left in another room adjacent to the play room...  there wasn't a spare there to place it & I was too slow to place it in the bathroom.  This happened in my first year of hobbying.  Now, I hope I'd keep my composure enough to remember the placement.  Frankly, I was stunned by her beauty...  so I hope she's made some allowance.  
HV