Yes in the few years since I started building accordions every set as for as I can remember has had one and not just set of C reeds even C#, D and E. In these three pics I took the top two pics are of two seperate sets of C reeds its the second from the bottom reed and on the set of E reeds (bottom pic its the third from bottom. I dont know why Ive ask couple other builders and I havent found anyone that knows why. Im just kinda of curious as well

Do your reeds come from Martins as well?, on Bincis website there is no mention or pics of reed sets with a single brass reed?

I do get most of my reeds from Martins but a few other builders I know all are aware of the same thing and they order reeds from binci themself. The only set that I can remember that didnt have that one brass was an older set. I dont know how old the set was and dont have a way of knowing what year they where made.
I did just get off the phone with Larry Miller and he said "to his understanding" it was because brass is harder and that harder reed base it helped that smaller reed tounge respond quicker. I ment to ask him where he got that info from but What I dont understand is why not make the very bottom reed base brass also.

Excellent point, It just bothers me having a brass reed now after 40 years of playing and not having one before. The Ciccarelli are all brass bass, but I am not partial to their tone, if I find a better answer I will let you know also .

A lot of sets, if not most, have brass on the 2 smallest (highest) reeds, because they are notoriously hard to start and brass apparently helps that. Even some that may look all aluminum have those 2 reeds with brass bases, and plated to match the other reeds, I guess.

Ciccarelli are not necessarily brass bass reed bases. They come however they are ordered, and you can order them in all or a combination of brass or aluminum. Harmonkas reeds in the Czech republic, make a Saxony reed copy (like what was put in the old Sterlings and Monarchs) that even offer zinc as an option, which is what the old reed bases were. I have some Ciccarelli in brass throughout, and like you, I'm not crazy about them, a little shrill.

It has been over 20 years since I have had a new accordion made & I guess things have changed in the industry just like every thing else made today. I will try to keep an open mind and ear and hope for the best. I know all musicians continue to search for that elusive holy grail in every instrument they play. I can say my Falcon dual melodeon is hands down my workhorse for the last 20 years.