Sorry about the delayed response. Just to clarify, I am talking about an alto piece. I have tried and own a lot of Meyers and Meyer copies. I currently have in my Meyer collection :
2 NY USA 8Ms (one is the older model with more scooped side walls)
NY LTD 6M
early Babbit 5M
and a 6M USA (which was my main piece all through college).
Meyer copies I have are:
GW NY 7 touched up by MOJOBARI (this piece actually plays the closest to the Bros)
SR Tech L85 (clear and HR)
I've tried a few others over the years. Most of the pieces play very similar. Can't say there is a bad playing piece in the bunch. So as far as my experience with other pieces, I feel I have a good bit of it. I don't have measuring tools so I can't tell you exact numbers, but most of my pieces are around .85, other than the smaller Meyers, and they play similar but don't need as much air.
So they Bros I played measured around .70. It had similar sidewalls to the older NY 8M and the GW NY 7. It just played VERY well. I could take the tone anywhere I wanted. It was very versatile. And it was very consistent throughout the range of the horn. I could get a great throaty sound as well as a nice smooth tone, altissimo was easy and brilliant. It really was what I had hoped a Bros would be. It met my expectations. I'm working on getting it.
So considering all the other pieces I've tried, most with very similar specs, my only conclusion must be that it has something to do with the rubber. I have heard this from many sources as well. Something to do with higher sulfur content. I'm not the expert though and only basing this on my personal experience.