I am not very knowledgeable about binocular glass, but I will say this. My old Pentax 10x42 DCF WP binocular with phase coating that is made in Japan has kept me from experimenting. I bought these from camerland about 15 years ago (or more) I think.

Faith and love of others knows no mileage nor bounds. That's simply the way it is.
dogzapper

After the game is over, the king and the pawn go into the same box.
Italian Proverb