German hoppers Castor, Mars, Jupiter and Pollux built at Schiedam, Netherlands according to the Dutch newspaper Schiedamsche Courant dated 24September 1912

An item reported the intended launching next day at the shipyard Gusto (firm A.F. Smulders), Schiedam, Netherlands at 15.00 o’ clock. The edition a day reported the launching of the steel made hull of a seagoing hopper, the last of four built for foreign account. She was baptized by Miss Truida Dekker. Dimensions 44 x 8,80 x 4,40 metres. Hopper capacity 400 cubic metres. To be fitted out with 1-300 ihp triple expansion engine and a boiler with a heating surface of 100 square metres and 13,5kg pressure. Further more the necessary steam winches for lifting anchors and manoeuvres. Would go under own power towards her destination. (1)

Note
1. The yard numbers 438 (Castor) and 440 (Mars) built for Habermann&Guckers, Kiel, Germany and the 439 (Jupiter) and 441 (Pollux) built for V.d. Velde, Kiel, Germany.