I am not 100% certain on that, but I believe the caps on that master cylinder would have been unmarked. The same cap was was used on '70 disc brake E bodies and was marked with instructions to use SAE J1703 brake fluid, I've seen NOS '70 style MC's with date codes into late '71 or early '72 that had the callout, after that they were unmarked. It is possible that '71's through a certain date had that callout but I have looked at a number of them and never seen one with any markings.
As for the finish, my research indicates that starting in '71 they changed from painting the entire master cylinder assembly black, to using some sort of a gunmetal gray phosphate type coating as shown in this picture of an NOS one.