Entry in progress—B.P.
     
Google Books
The Wheeler Dealers
By Adam Smith
New York, NY: Bantam Books
1969, ©1959
Pg. 176:
Son, when the market is goin’ up everybody looks smart. Never confuse brains with a bull market.
ANON
 
2 December 1980, Chicago (IL) Tribune, “Money Management” by William Gruber, pg. C3:
A WELL-KNOWN Wall Street stock analyst says his boss is wearing a button these days reading, “Don’t confuse brains with a bull market.”
     
Google Books
Life and Death on the Corporate Battlefield:
How Companies Win, Lose, Survive
By Paul Solman and Thomas Friedman
New York, NY: Simon and Schuster
1982
Pg. 207:
But Dean LeBaron has a button he keeps on his desk. It reads: “DON’T CONFUSE BRAINS WITH A BULL MARKET.” 
 
24 March 1986, Doylestown (PA) Daily Intelligencer, pg. 15, col. 1:
In any event, he concluded, one old Wall Street maxim certainly applies: “Don’t confuse brains with a bull market.”
 
14 March 1987, New Mexican (Santa Fe, NM), “Taking stock” by Michael Armstrong, pg. C1, col. 1:
“Don’t confuse brains with a bull market.”—Humphrey Neill.
       
New York (NY) Times
Mutual Funds; An Old-Timer Suddenly a Star
By CAROLE GOULD
Published: January 12, 1992
William M. B. Berger, a Denver money manager with a superb five-year record, was discovered by investors in 1991, and his biggest fund’s assets increased more than tenfold.
(...)
The 66-year-old money manager takes all of this in stride. Last spring, he handed out buttons to his staff that read: “Don’t Confuse Brains With the Bull Market.”