Hello - I am new to this forum here, hope you don't mind my reactivating an older discussion.
I thought I give you some first hand information or confirmation on the question of B6s and 990 Yanis with a badge like the 880.
I own a T990 that exactly has the Yanagisawa coin/badge that we know from the 880 horns. I assume that these were the first 990ies and that Yanagisawa changed to the engraved name after the badges/coins have been used up. (this is only my personal speculation)
Regarding the earlier discussion on the B6 Baris - I also own 2 B6 Baris - one has the "old" keywork on the bell keys the other has the more modern looking style of the 900 series.
If requested I can provide pictures of all 3 horns.