23rd June 1991
|1991 Sc1||1992 Sc25 † SG4||xxx|
imperf, no wmk, lithographed
perf 12, no wmk, lithographed
Printed at Chisinãu
Printed at the Russian State Printing Works, Moscow
† Scott did not at first recognise the 1991 issue and began with Sc25.
|7 kopeks green and multi||1||1|
|13k blue and multi||2||2|
Originally Moldavia, a republic within the Soviet Union, in 1990 Moldova declared sovereignity within the USSR and became independent in 1991.
Dniester, Pridnestrovian Moldavian Republic, PMR, Transnistra
Wikipedia  states, “ Transnistria (also called Transdniester, Trans-Dniestr or Transdniestria) is a partially recognized state located mostly on a strip of land between the River Dniester and the eastern Moldovan border with Ukraine. Since its declaration of independence in 1990, and especially after the War of Transnistria in 1992, it has been governed as the Pridnestrovian Moldavian Republic (PMR, also known as Pridnestrovie), a state with limited recognition that claims territory to the east of the River Dniester, and also the city of Benderand its surrounding localities on the west bank, in the historical region of Bessarabia. The names "Transnistria" and "Pridnestrovie" both refer to the Dniester River.
Unrecognised by any United Nations member state, Transnistria is designated by the Republic of Moldova as the Transnistria autonomous territorial unit with special legal status or Stînga Nistrului ("Left Bank of the Dniester").
After the dissolution of the USSR, tensions between Moldova and the breakaway Transnistrian territory escalated into a military conflict that started in March 1992 and was concluded by a ceasefire in July of the same year. As part of that agreement, a three-party (Russia, Moldova, Transnistria) Joint Control Commission supervises the security arrangements in the demilitarized zone, comprising twenty localities on both sides of the river. Although the ceasefire has held, the territory's political status remains unresolved: Transnistria is an unrecognized but de facto independent presidential republic with its own government, parliament, military, postal system, and currency.”
Gibbons  comments at length on the origins of the PMR, expresses uncertainty over the stamps issued and states, “it is likely that the issues will be included in future editions of this catalogue”
The latest piece in the journal is v22n3p4 by Tim Balm, The First Issues of Transnistra - Revisited
There is a site devoted to PMR here.
More research will be done.