The master cylinder cover that came on the original master cylinder was also sent out to be restored. The pitting was too severe though and it’s not OK for a show car.
A very well known former GM engineer that uses the screen name JohnZ has had a few postings where he states that the correct cap for a 69 Z does NOT have “SAE J1703” on it. It should only say “USE DELCO BRAKE FLUID” and “SERVICE WITH DELCO PARTS”. He posted a picture of his cap:
His 1969 Z/28 cap is identical to my 1969 Z/28 cap except that his looks very very very nice.