Need to ask about a lot?

RUSSIA - 1940 1940 Death Anniversary of Timirjasew complete set of four, (SG 906/909, Michel 749/752), in strips of three affixed to part of an archive sheet, each cancelled with red three line 'SPECIMEN / COLLECTION / MAURITANIE' handstamps. Signed and numbered in black ink 'St Louis 19/1/51'. Unique item from the Mauritania Post Office UPU Specimen collection. (12 stamps)