it's a Hammerhands, which is intended to be a precursor to the Warhammer. 3/5/3, paired AC/10s, lots of ammo. fun in a city.
That is a nice 'Mech, although the range is a bit limited and the strategic mobility is not as good as the later designs.
Also, I am loving these posters, I just wish I had some of my own to contribute.