Tabaristan, on the southern coast of the Caspian Sea, was about the last area in Persia to be conquered by the expanding Muslim Empire (because
of the inaccessibility of their territory), finally yielding in 761.
Even after being conquered it was still powerful enough to mostly operate autonomously. Tabaristan was so prosperous from trade with the East and with
Europe that these coins have been unearthed as far away as Denmark and Sweden.