I was somewhat surprised that such obvious deposits got by NGC. So, I cracked open the slab and gave the coin an acetone bath (100% concentration). Now, the deposits appear to be gone. The bath was about 10 minutes long, followed by a rinse with distilled water. ATTICA, Athens, Circa 124/3 BC AR tetradrachm (28mm, 16.85 gm) New style coinage MIKIΩN, EYPYKΛEI and ΣΩKPATHΣ, magistrates. Helmeted head of Athena right / owl standing right on overturned amphora, head facing; To right, the Dioscuri standing slightly left; Letter E on amphora, ME below; All within a wreath. Thompson 483 Good VF with a generally well centered strike. I think this coin would not have been slabbed by NGC, had they known about the PVC deposits. Has anyone had similar experiences?