The Kyiv #3 Overprint Series
Grigory Lobko, a Ukrainian philatalist, conducted his own investigation of contemporary trident overprints, and he published a Catalog (1996) of his findings. According to Lobko, the oblasts or provinces that issued trident overprints include Zaporizhya, Melitopol, Kyiv, Lviv, Mikoliyiv and Chernivtsi.
One of the most commonly available set of overprints is classified by Lobko as Kyiv #3. My German-made Lindner stamp album for Ukraine includes a page titled "Lokalausgaben" for displaying this twelve-stamp series.
Three different Soviet definitive stamps were used for the Kyiv overprints.
Note that the 50-kopek overprint occurs on two different stamps, Lobko Catalog numbers 29 and 31. Altogether, these twelve overprint varieties compose the Kyiv #3 series, Lobko Catalog numbers 23 through 42.
Out of the twelve major varieties spring a number of additional varieties. In the lower denominations, each sheet of 100 stamps contained eight stamps with the trident shield reversed. Higher denominations -- the 10, 20, 30 and 50-karbovanets overprints -- do not feature this variety. Other variations are noted by either the location or appearance of the values in the overprints.
Most of the trident stamps that I've seen are in mint, never-hinged condition. Postally used specimens seem to be relatively rare. I have several postally used overprints and only one envelope with a paper provisional imprint actually glued onto it. As a collector, I think that this makes the postally used specimens an interesting find.
There are many forgeries of these overprinted Soviet stamps in existence, and I urge any prospective buyer to be very careful.