Doug, good that you did not find out you had an issue the HARD way.... brake failure can be a heart stopper... been there done that ...!!! That you have lost fluid kinda takes master cylinder out of the mix, unless anything is visible by way of fluid around it... If you have a servo (?) I have known fluid to leak into them, which can be picked up on the dip stick as dots of fluid, a bit like water in the oil. My bet would be on a wheel cylinder or less likely calliper piston... though at the age of your car corrosion on brake lines could perhaps be an issue. I would start with the rear brake cylinders.. if they have leaked you might also need replacement brake shoes as they will be contaminated... Though I have in the past burned the oil out of the shoes with a blow torch as a temporary measure when replacements were not to hand.... but then I can be a bit stone age mechanically at times (-:
Good luck.
