Mexico City, Mexico, cob 1/2 real, Philip V, assayer F, mounted cross-side out in 14K gold bezel with shackle bail. 4.02 grams total. Sea salvaged piece though unknown as to what wreck it is from, bold partial monogram and cross both a bit off-center, clear mintmark and assayer with partial date 173(?).
Estimate: 250 - 375 USD