Thanks for sharing, very nice having someone building something similar
I am not a very experienced road cyclist, I only have two bikes in present time, and I am not a big "conoisseur" of brands, frames and so on, but I am quite happy to be learning many things regarding road bikes. And I´m particularly dedicated to this Giant. I emailed Giant Europe to seek info about my frame, sending them the serial number, unfortunately they do not have a database for "older" bikes.
I´ve edited first post with a pic of how the bike was the day I bought it. Yes, from everything I´ve searched, TCR´s and OCR´s at that time were quite similar. As you said, I also believe my frame to be a bit "unique" due to race number hanger and engraved Once logo on the dropouts. I will post a pic later on. Please feel free to share anything regarding your current project, or your other Giants.