The Tank Solo has several differences from my watch. Mine is the Tank Louis Cartier XL from the (in Cartier speak) "Retired" CPCP collection. It was at the time, the largest classic Tank Louis Cartier model produced, had a hand wound rectangular movement from "Sister company" Piaget, that could be viewed through a sapphire case back. The guilloche dial with "Rose"design at the center is unique to the CPCP watches. In addition they were made in small numbers. IIRC they made 200 in pink gold and 50 in platinum.
The Tank Solo's have a more common and less expensive ETA based movement, a solid steel case back, the top side pieces of the case are flat not rounded, the dial is different, and it's far less expensive. It's also a current production model.
There is currently a Tank Louis Cartier XL Extra Flat, that is closer in design to mine than the Solo, It's slight larger than my watch, but thinner due to its very fine, ultra thin manual wind movement. It's movement is higher end than the Solo's movement. It has a gold case and gold case back, and the tops of the side pieces are rounded like on my watch. It has has a silver dial, but without any guilloche design. It's significantly more costly than the Tank Solo.
Each of the current pieces is quite nice, its simply a matter of which you prefer in terms of design and price. I suggest trying on each, as the dimensions are different and they may fit you differently. Keep us posted on your research and good luck. Cheers!