You have a 2% chance of getting any given piece. The first piece you get, by it’s very nature, would be unique. The next piece would have a 2% chance to be a repeat.

IIRC, you have to find an average of 100/RemainingPieces pieces found in order to get a new piece, so it should take an average of 225 pieces found in order to complete the file.

I’ve gone ahead and created a spreadsheet, so if you want to know about how many new pieces it’ll take to complete the file then just ask here.

Also, if anybody can tell me what the drop rate is for the file in HOFF then I’ll also be able to tell you the average number of visits it’ll take, too.