Before the HTC One Max was officially unveiled, there were a few leaks showing a dual-SIM version. It showed up in Vietnam, although it was supposedly a unit headed for the Chinese market. It cost 21.6 million dong ($1,015), up from 17.9 million dong ($840) for the single-SIM version.
The specifications look exactly the same – 5.9" 1080p screen, Snapdragon 600 chipset, 4MP UltraPixel camera without OIS, 16/32GB built-in storage with microSD card slot and 3,300mAh Li-Po sealed battery.
Except, of course, for the second SIM slot that's positioned symmetrically opposite the first SIM slot. The labels indicate that the first SIM is 3G-enabled, while the second SIM is 2G-only. The One Max has 4G LTE too and presumably that's SIM1-only as well.
There's no info on when – of if at all – the dual-SIM HTC One Max will make its way to the international market.
Source (in Vietnamese)