This shelf is used from 8/65 till 7/66 as part of M-code 620 when the 12Volt wiper motor 211955113D is used.
Thick lip parcel shelf.
Difference could be that some are mounted with 3 and others with 5 screws.
The parts manual displays only the number 211805207 but there are differences in the parcel shelf.
There’s a thin lip, thick lip and a thick lip shelf with dent for the big 12V wiper motor with 2 speeds.
The shelfs could be mounted with 3 or 5 screws.