Upgrading items to unique items found in chronicle sheets

[ioosef]

If I remember correctly, you're allowed to slowly upgrade an item into a named item, such as celestial armor (for example, a pay the price difference between a +3 chainmail and celestial armor to turn that +3 chainmail into celestial armor). Assuming that's still the case and I'm not mistaken, can you do the same with unique items found in chronicle sheets? Items such as the ones found in

Spoiler:

Gamin in Night March of Kalkamedes or Corpselight Rapier in the chronicle sheet for the Prince of Wolves book

Once you get said chronicle sheet and access to said items for purchase, can you slowly upgrade your way up to them as opposed to buying them all in one chunk?

[Tony Lindman]

Unique items are just that - unique. I would not expect that the campaign leadership intends you to be able to do that. Unless Mike or John explicitly say you can, I would recommend you not plan on it.