It is probably 40 plus years old.... It's old, rusty & if it hasn't started leaking it will!
 
Available for dual or single disc
DOT 3 or 4 brake fluid only
Cap & Float included
 
FITMENT:
14MM - 1974-1980 R75/6, R90/6, R75/7, R80/7, R100/T, R100, R100S, R100RS, R100RT
16MM - 1974-1976 R90S 
17MM - DUAL DISC CONVERSION, R100S, R100RS, R100RT