I think the lore is backwards for the Finished and Unfinished slivers.
The sliver you loot from Ikky4 has the lore "Show to Tublik...". Once you cycle it thru Tublik, and he tells you to go to the NPC in Abysmal Sea, the lore changes to "Two pieces fit this one..".
Since unfinished vs. finished are Alla things, it would seem to me that the Unfinished one is the one before cycling thru Tublik, and the Finished one is the one after cycling thru Tublik. They are backwards here.