603DX:
Well, I qualified just before you on 04.07.57 and my "A" and "B" was issued (No.23584) on 05.07.57. The signatures of Lord Brabazon of Tara and Yvonne Bonham look like rubber stamps as does the "C" and "Silver C" stamps by Frances Leighton.
The first "genuine signature" appears to be Naomi Christy on my "Gold".