I have a similar coin. I found only this on the web about it:
"These coins are quite unusual. Minted by the Mamluks of
Egypt around in the 14th century they are extremely thick.
The only other coins of equal thickness are some of the
ancient Greek and
Ptolemaic Egyptian. The
reverse can
contain
Islamic script but can also be blank. The
obverse bears a distinct rosette. These coins puzzled researchers for
years and are nice examples of the
type."
if you
google "mamluk rosettes" you may find few pics also. The
ottoman origin is reasonable also as mine came up in the northern
part of the former
ottoman empire. (however, the drifting of coins is an ever increasing mystery as my
collection grows...)
