The box they put my old parts in says "Anderson Power Products, Div. of Anderson Interconnect, Inc., 13 Pratts Junction Road, Sterling, MA 01564,
These folks are at www.andersonpower.com - searching for "6319" will lead you to the right catalog page. 6319G1s come in gray or red. The gray ones are for 10/12 AWG wire, and the red ones are for 6-gauge.
Interestingly, I just ran across these connectors myself (or at least their twins - they look identical). They are used to connect the battery in the UPSes I use for my Unix machines.
