Hi,
Thanks for the questions.
I personally don't put wallets in my back trouser pocket but it would definitely fit as it's just larger than a credit card. The leather is soft, so I imagine it would be comfortable.
I usually keep just a single £1 coin in there, for the shopping trolley at the supermarket, and so far there's no indentations shown. You can see the diagonal lip of the internal pockets appear on the leather, and having looked at YouTube reviews that does seem to be usual for this leather, which is soft but developing a nice shine, compared to when it was brand new.
I still really like this and bought another one for my brother for his holidays. It's small but has a great deal of capacity, and the zip of course means it's very secure but quick to open. The zip has worn in and is now very smooth.
Here are a couple of shots, with a month and a half of use.
And a final shot of the capacity. Going left to right, you can see the top of the deep coin pocket, the middle section with 5 cards and the tile tracker which counts as 2 cards, then the cash pocket with 2x£10s and a fiver folded in thirds. You could easily add another five cards, or more notes or coins. You may also be able to make out a final feature on the right lip, a space for a SIM card. Not something I've needed.