Not sure about the smallest silver, but there were fourrée /
plated imitations of even the earliest
electrum coinage, including very small
denominations. I'm not sure if I've seen a
plated 192nd
stater, but I've seen multiple fourrée 48th staters advertised for sale/auction and at least one or two 96th staters.
CNG recently sold a fourrée Phanes 1/48
stater at 5mm and 0.27g (EA 511, Lot 115). Last year Heritage sold a
plated 48th of the plain globular/punch variety at 5mm, 0.26g (
ACSearch LINK), and in 2020 a slightly smaller Alyattes 1/96th
stater at 5mm, 0.20g (
ACSearch LINK)! I only see one record (
LINK) advertised as a
fourree tetartemorion (no hemitetartemoria), from
Agora 35 (in 2015), Lot 71,
Caria,
confronted bulls, 7mm, 0.40g. (
EDIT: I see it's the one Altamura referenced above!)