The T1-series utility droid refers to a line of maintenance droids that were produced by Duwani Mechanical Products. These droids were available before the T3-series utility droid came onto the market.
Before the Great Sith War, Kellenech Technologies originally manufactured the T1 series of droids, specifically the T1-series bulk-loading droid. However, the company went bankrupt in the years that followed. Its assets were sold off, and Duwani Mechanical Products acquired the T1-series trademark.
Duwani Mechanical Products, the new trademark holders, began producing their own line of utility droids under the same designation, resulting in Kellenech's original T1-series becoming widely recognized as the "LB"-series to distinguish it from the more recently produced model.