The Aircraft Flash form went through 3 versions throughout the run of the Ground Observer Corps (GOC). The first was AF Form 6-2 in 1950.
This form was probably only issued for a year as in 1951, the updated Aircraft Flash Message Form 6-3 was issued. Observation posts probably used whatever forms they had until they were gone and then were issued the most up to date form.
The form seems to have been updated last in 1955 with the updated Ground Observer’s Guide.
I have an original book of Form 6-2 and there is probably about 100 forms in the book. Given how infrequent sightings were in some areas, I wouldn’t be surprised if a post went through less than a whole book a year. Thanks to my friend, James Foreman, who is a collector of WWII Air Warning Service material who alerted me to the eBay listing, as it was incorrectly categorized as WWII. The book comes from Hooper’s Island, VA, which built an observation post in WWII and reactivated it in 1950.