The last diagonal brake split models had this square plastic canister (reservoir). With metric unions it's recognized by the rectangular reservoir and small cap with a switch in the body, but regretfully the switch is obsolete and all attempts to remanufacture at AP Raicam have failed- HAS A BLANKING BOLT FITTED
Fitted end of 1975 to 1980 with few export markets to 1982.
Most Canadian and many export model Minis had a dual brake system of some sort and earlier cars had "imperial" fittings but this has metric unions. Fitted from late 75 to 1980 in Canada and you can change the brake pipe ends to metric for use.
Ensure the correct DOT4 or DOT5.1 brake fluid is used as these cylinders are not designed to use anything else such as Castrol SRF for racing or any mineral fluid.