WMS or Williams Interactive were founded way back in 1943 and like Bally were renowned for making Pinball Machines! Their HQ is in Chicago and in the mid 1990’s they began to produce slot games for land-based casinos and later moved into the online arena, initially reproducing digital versions of their cabinet videoslots. They created the now defunct Jackpot Party casino (taken over by Slots Magic) for the UK market and since then their games have become hugely popular in Europe as well as North America. In 2014 they completed a merger with Bally and now operate under the SG (Scientific Gaming) label which also includes Barcrest and other smaller developers. Their popular slots include Bruce Lee, Raging Rhino and Ruby Slippers.  See the full list of WMS slot titles and RTP percentages here.