The earliest Pentax 6X7 was produced in 1969-1971. These cameras have some differences with the next cameras produced in 1971-1976.

Most notable differences: a) film advance lever; b) film type switch

Most notable difference: a) curvature of winding lever; b) film type switch “10/21” vs “120/220”

So, the earliest cameras have pan head screws (not Philips), round spring loaded locking lugs underneath. Some differences disappiared gradually while production. But there is another notable difference on really earliest cameras: the film type switch was marked as “10/21” shots instead of “120/220” film types on the next cameras. Yes, the earliest Pentax 6X7 was able to make 21 shots on 220 film type. But the film transport was poor, frame space was very unstable and camera continued to produce but with film transport for 20 shots and the switch was marked as “120/220”. Many cameras were returned to Asahi for fixing the problem and modify they film transport for 20 shots.

Early Pentax 6X7 locking lugs difference

Top image: locking lugs of early cameras. Bottom image: next cameras since 1971

Another notable difference is the single red dot mark for 120 and 220 films. After some time the film transport was changed due reliability and the single red dot mark was replaced by two separated marks for the 120 and 220 films.

Early Pentax 6X7 film transport difference

Left: early Pentax 6X7 with single dot mark for 120/220 films. Right: next camera version with two separate marks for 120/220 films

Film plate on early models did not have additional spring roll that makes better film friction with the special rubberized roll that do proper film transport and shots counting.

Early Pentax 6X7 preassure plate diference

Left: early Pentax 6X7 preassure plate with only one spring roll. Right image: modified film plate with additional spring roll and 120/220 direction marks

Many earliest cameras are really old and heavy “worn”.