It's all the letters along that column. There's a weird artifacting that bolds everything along that line.

I seem to remember a swinging arm that I would click in place after inserting a 5 and a quarter floppy. I do think the 3 and a half floppies ticked a little when you pushed them into the drive, but not nearly so much as clicking the arm in place for the larger ones.

Pretty sure the first floppies were 7", but there weren't in use for very long. But, I would agree with your assessment regarding the two sizes most of us were familiar with.

the p tank is full