The date of Jacobus's consecrated is uncertain, but that given by Assemani (AD 541) is probably correct.
Commentary on the weights and measures of the Bible and the Talmud (Vatican MSS., No. 298, 4; see Assemani, "Catal." p. 283; Steinschneider, "Joseph ibn Aḳnin", in Ersch and Gruber, "Encyc." section ii., part 31, p. 50; "Ginze Nistarot", iii. 185 et seq.).
De Rossi (Parma MS. No. 68, 8) declares the author's name to be doubtful, since the manuscript is anonymous; but Assemani (Catalogue of Hebrew MSS. in the Vatican Library, No. 235) concludes that its author was Shem-Ṭob of Soria.