I started a separate thread about this for trivia purposes, not realising this thread existed. I believe I have the official list of Balmain and Magpie players pre 2000, cross-checked against Rugby League Project.
Columns are
Debut year | Balmain or Wests first | Matches for Balmain | Matches for Wests | Played for other clubs? (i.e. no clubs other than Balmain or Wests) | Filter for dual players (always = 1)
1990 B 13 31 N 1 AFFLICK, Mark
1991 B 12 23 Y 1 ANDERSON, David
1976 B 4 57 Y 1 BEAVEN, Mark
1983 W 4 40 Y 1 BEAVEN, Paul
1980 B 4 38 Y 1 BILBIJA, John
1976 B 20 96 N 1 BOLAND, Warren
1957 B ? ? N 1 BRAY, Ken
1938 B 6 ? N 1 BROWN, William
1915 B 37 2 N 1 BURNICLE, E
1913 B 22 28 Y 1 BURNS, P
1908 B 1 15 Y 1 CARROLL, Pat
1983 W 4 6 Y 1 CARTER, Matt
1951 B ? ? N 1 CHURCH, Ernie
1981 B 1 24 N 1 CLARKE, Craig
1959 W ? ? Y 1 CLEGG, Frank
1976 B ? 11 N 1 CLOUGHESSY, Bill
1992 W 2 7 Y 1 COCHRANE, Evan
1936 B 6 4 N 1 COLLESS, Dave
1981 W 98 34 Y 1 CONLON, Ross
1976 B 23 50 Y 1 COX, Greg
1915 N 62 32 Y 1 CRAIG, Jim
1985 W 11 29 N 1 CROOKS, Lee
1976 B 11 2 Y 1 CROWE, Gerard
1983 W 67 28 Y 1 ELIAS, John
1977 B 1 1 N 1 ENSOR, Col
1943 W ? 11 Y 1 FAYERS, Fred
1923 W 5 63 Y 1 FIFIELD, Cecil
1983 W 99 16 1 GALE, Scott
1952 W ? ? N 1 GOFF, Bede
1971 B ? ? N 1 HANDCOCK, Peter
1988 B 34 13 N 1 HANLEY, Ellery
1961 B ? ? N 1 HANSEN, Bill
1923 B 52 19 N 1 HAYES, Les
1955 B ? ? Y 1 HENDERSON, Brian
1977 B 14 10 Y 1 HILLIARD, Bill
1951 B ? ? N 1 HYDE, Pat
1981 W 243 5 N 1 JACK, Garry
1912 B 76 9 Y 1 JOHNSTON, Albert
1979 B 16 3 N 1 KERR, Steve
1940 W 10 2 N 1 KINNARD, J
1972 W ? ? Y 1 KNIGHT, Stephen
1979 B 56 4 N 1 LAWSON, Mark
1920 B 25 8 Y 1 LISTON, Roy
1974 W ? ? N 1 LIUBINSKAS, Mick
1917 W 31 2 Y 1 LUCAS, Bill
1985 W 45 16 N 1 McFARLANE, Gary
1988 B 15 23 Y 1 McGARRY, Damien
1921 W 12 147 N 1 McMILLAN, Frank
1961 B ? ? N 1 MacDOUGALL, Gil
1929 B 11 4 N 1 MAGNUS, Tom
1974 B ? 42 Y 1 MOUNTIER, Arthur
1968 W ? ? Y 1 MURPHY, Tim
1983 W 97 47 Y 1 NEIL, Michael
1983 B 6 30 Y 1 PETHYBRIDGE, Rod
1913 B 56 1 N 1 POTTER, George
1969 B ? ? Y 1 PRATTL, Olaf
1982 B 1 6 N 0 RIGNEY, Scott
1943 W ? 26 N 1 RUSSELL, Jack
1972 B 65 2 Y 1 RYAN, Trevor
1971 B ? ? N 1 SATTERLEY, Stephen
1985 B 47 9 N 1 SCHOFIELD, Garry
1997 B 10 1 N 1 SCOTT, Marshall
1930 B 20 24 N 1 SIMPSON, Stan
1935 W 96 45 N 1 SMITH, Athol
1947 B ? ? N 1 SMITH, Bruce
1953 B ? ? Y 1 SMYTH, Kevin
1958 B ? ? Y 1 TONKIN, Bill
1912 B 96 16 Y 1 WALL, Lyall
1979 B 37 36 Y 1 WEBSTER, Gary
1976 B 132 14 Y 1 WIGHAM, Wayne
1949 W ? ? Y 2 WILLIAMS, Jack
1972 B ? ? Y 1 WORTH, Russell