20mm Type 100 AP-T?

Just picked up what I believe is a Japanese 20mm Type 100 AP-T round. There are green and white stripes on the blackened bullet, and remains of red around the driving band and case mouth. There is a single Japanese character at 6:00 and an etched number (.784) at about 1:00. Any comments on what I have and an approximate value would be appreciated.

Further, it has a 124-ish mm case.
Any thoughts on the significance of the red around the case mouth, visible for about 1/4" above and below the joint?

Is this of any help?..japaneseammunition.com/start … ub_cat=136