Built in 2003, by Thoma-Sea Boatbuilders of Houma, Louisiana (hull #121) as the HMS Frontier for Harley Marine Services of San Francisco, California. The tug was later chartered by the Signet Maritime Corporation of Houston, Texas. Where she was renamed as the Signet Challenger. Powered by two Cummins QSK60 diesel engines, with two Rolls Royce US205 z drives, fitted with two 84.6(in) by 78.6(in) four bladed NIBRAL propellers. For a rated 5,250 horsepower. Her electrical service is provided by two 95kW/60Hz/208V Cummins 6BTA5.9 generators. The tug’s capacities are 107,000 gallons of fuel, 5,000 gallons of water, 500 gallons of lube oil storage, 500 gallons of hydraulic oil, and 1,000 gallons of dirty oil storage. The towing equipment consists of a Markey DYSF-42 winch, mounted on the bow. Outfitted with, 430(ft) of 2.25(in) Samson Saturn-12HMPE hawser. On the stern she is fitted with a single drum, 100 horsepower, CME Model 1M160-200D7-1257-130 Single Drum towing winch. Outfitted with 2,000(ft) of 2(in) towing wire.