Watch List notes:

Divus Constantius I. Died AD 306. Æ Follis (24.5mm, 6.45 g). Restruck brockage. Londinium? (London) mint. Struck under Constantine I, AD 307-310. DIVO CONSTANTIO PIO, veiled, laureate, and cuirassed bust right / MEMORIA FELIX, incuse and reverse of obverse and lighted and garlanded altar; [an eagle standing on either side; PLN]. Cf. RIC VI 110 corr. (no mention of cuirass, but the plate clearly shows it); cf. C&T 5.04.010. Brown surfaces, major roughness on obverse. VF.

Brockages occur when a coin remains in the die after striking and another blank is then struck, leading to a deformed, incuse image on the second. Ancient mints were usually not concerned with this sort of flaw, and brockage coins appear to have circulated as regular strikes. Occasionally, coins appear in the market described as "restruck brockages" or "overstruck on a brockages." Most of these are in fact die clashes, which occur when the dies strike one another without a blank between them. That the present example was restruck indicates a significant level of quality control at the mint, and that mint workers caught the error after it was created, and place the coin back on the dies to correct it. For further discussion on brockage coins, see: J. Nurpetlian, "Brockage Coins," in NC 2018, p. 225-245.