The Stavraton denomination
The Stavraton was a type of silver coin used during the last century of the Byzantine Empire. They were large silver coins introduced by Emperor John V Palaiologos in circa 1367 and used for the last century of Byzantine history.

The coin was designed to replace the defunct gold hyperpyron as the highest-denomination coin in circulation. Hence it was made heavier than any previous Byzantine silver coin, or, for that matter, any contemporary European coin, weighing initially 8.5 grams but falling later to 7.4 grams. It still had only half the value of the hyperpyron however, which remained in use as a notional currency.

Fractions were also struck - the half-stavraton initially weighed 4.4 grams and gradually declined to 3.7; the one-eighth, known as the doukatopoulon or aspron, weighed circa 1.1 grams. Quarter-stavrata were not minted.
Stavraton

(1) John VIII 1421/5-1448
Obverse: IC-XC, Facing bust of Christ, right hand raised, eight dots around surrounding
Reverse: WANHC DECPOTIC O PALEOLOGOC QV XAPITI AVTOKPATOP in two lines around nimbate facing bust of John VIII; dot to left and right.
Ref: Sear-2563