**3. Experimental Methods and Tests**

Because of the rareness of the Yehud silver coins, invasive analysis of the objects was not permitted; thus, the coins were studied by using non-destructive testing (NDT) methods:


were locally ground in different areas with 240–320 silicon carbide grit papers to reveal their bulk metal composition. The examined coins were IAA 153976 and IMJ 27424 (Type 5 O1/R1), IAA 101006 and IAA 154383 (Type 5 O1/R2), IMJ 27383 (Type 16 O2/R2), Trans-Jordan 11 (Type 24 O1/R2), and IMJ 34591 (Type 31 O1/R1). The composition of these coins was detected in several areas before (Supplementary Materials, Tables S1, S2 and S6–S8) and after locally grinding their surface (Supplementary Materials, Table S9).
