Hi Paul,
They are 1966 MKIV Zephyr units. I've found a couple of sets over the past few years but they are getting as rare as rocking horse poo. When the MKIV was facelifted in 1967 they went to the eyeballs with the closeable flap incorporated - as found in the MK III and IV Cortinas and the MK II Escorts. I've been asked by several people to keep alook out for some, but my recent searches have proved fruitless.
Cheers,
Brian.