The pics make that disk look exceptionally new and fresh. Unfortunately the number 1 in the roll number and the number 1 in the company are the same stamp, they should not be and raise a red flag for me. This being such a rare unit it screams fake. If you look at the other disk posted you can see how the blood type and the roll number are in different stamp sets than the rest of the disk.
Great thank you, that sums up my concerns! The mention of the font differences is a big help, it's something I didn't and wouldn't have really noticed before, obvious now though. Thanks again to both of you for your help. I'm going to leave it I think
Being sans serif font is not a good indicator. I would pass on this if offered to me.