Watch List notes:

The Eparch Collection of Roman, Byzantine and Islamic Weights
LATE ROMAN – BYZANTINE COMMERCIAL WEIGHTS

Circa 7th century. Weight of 3-libra (Brass, 84x23mm, 979 g), a very thick, discoid commercial-weight with a quadruple grooved edge (as MAH A12) and a recessed, flat top and bottom; centering hole on both sides, libra of 326.33 g. [ΛΙ] (the Ι curved) Γ; above, cross potent between two doves; all within a wreath with ties at the bottom; around, a low raised circular border and a high rim. Rev. Plain surface within a low raised circular border and a high rim. Cf. MAH 1 (a square 3 pound weight). Cf. CPAI 3, 2, 162 (for the edge). A piece of great rarity. Dark, olive green-gold surfaces with minor encrustations. Adjustment marks and old scratches, otherwise, nearly extremely fine.

From the Eparch Collection, acquired from a private collection in London.
Of exceptional interest, large weights like this are very rare; this is probably because they must have been very difficult to lose (as compared to all smaller weights) and were worth enough in their metal value that they would be melted down and reused for other things once they became obsolete. Bendall (p. 7) suggests that the libra weights with a curved iota in the ΛΙ monogram are earlier; however, Campagnolo and Weber (p. 35) suggest that they are later. In fact, the more cursive form does suggest a later date (in this case the 7th century rather than in the 5th or 6th).