Azerbaijan mail cover 1922

1922 registered cover (opened for display) from Baku to Teheran (addressed to the Russian Consulate), franked on reverse with block of 8x3000r including tete beche pair, with Meched transit and Teheran arrival postmarks, ms notation indicating "addressee unknown", letter returned back to Baku, some cover faults, otherwise fine and rare usage of a tete-beche on cover to Iran