After the German occupation forces pulled out of Estonia in November 1918, the Viru County Government ordered the opening of the Rakvere post office in the former tsarist Russian post office facility, which also housed the German Ober-Ost post office.
In rooms off to one side, the director of Rakvere post office, Aleksander Torn, discovered Russian-era postal band, postcards and postal stationery with pre-printed postage. The newly founded Estonian Postal Administration (Postivalitsus) had sent orders, but it was not yet possible to obtain Estonian stamps or permission for issuing local stamps. Torn thus turned to the county government for permission to overprint the Russian-era postal band, and duly received the go-ahead.
See the exhibition here