Rare... IMO no. Full removable top for 3 years, but 69-72 was also and IMO more valuable. It looks to be in decent shape for its age. But, I would scourer it for rust, Blazer bodies love it (tailgate, wheel wells, rockers, bottom of kick panels, and the front part of the bed which is directly behind the seats. In 78, the bed lost about 16" and became even with the front floor boards for more rear leg room. The seats are from a later model because in 77 the front seats were high backs. Looks like factory Spicer locking hubs which the vehicle didn't come with as it has the NP203 full-time t/case.
With that said, if the truck has little rust to no rust I would offer 3500 and leave at 5k tops. Its 50 years old and not that rare really. If it were a true survivor original paint, all interior, etc. that would be rare.
This was 12 years ago...
http://67-72chevytrucks.com/vboard/showthread.php?t=478426
Production numbers...
https://ck5.com/forums/resources/k5-blazer-specifications-1969-1979.9/
1973 - 44,841
1974 - 56,798
1975 - 50,548
1976 - 1st yr. 1/2 top - 74,389
1977 - 86,838
1978 - 88,858
Whereas the earlier years were...
1972 - 44,266
1971 - 17,220
1970 - 11,527
1969 - 4,935
I would imagine those are just Blazer numbers not including the Jimmy. Numbers rise through the years due to popularity.
In perspective,
https://myautoworld.com/gm/history/camaro/camaro1/camaro1.html#:~:text=First generation: Production 1967–1969&text=1967; RS: 64,842 --- SS,Z28: 7,199 --- Total: 235,147
67-69 Camaros -
1967; RS: 64,842 --- SS: 34,411 --- Z28: 1,002 --- Total: 221,306.
1968; RS: 40,977 --- SS: 27,884 --- Z28: 7,199 --- Total: 235,147.
1969; RS: 37,773 --- SS: 34,932 --- Z28: 20,302 --- Total: 243,085
1966-1977 Ford Bronco
https://broncobastards.com/blogs/hi...uction-numbers-throughout-the-years-1965-1996
During the 11 years, Ford produced exactly 207,347 examples of the first-generation Bronco. Ford sold most Broncos in its first production year – 23,776, and 1975 was its worst year with just 13,125 vehicles delivered to the customers. The modest production numbers, rust issues, and tough life that most of those Broncos had are primary reasons why the first generation is rare nowadays and sought-after by collectors.