On non-US non-rollbar vehicles this style of long jump seats continued up to 1976.
Then 1977-1978 are the same but with a folding leg in addition to the resting silent blocks.
And 1979+ no-more arm-rest and resting silent blocks, only the folding leg, and a slightly different shape.
If there is a trace of a cut-out armrest that would make sense. And some one added the legs to compensate the lost of rigidity (probably to use with an added rollbar?).
Not great pictures but what I found in my collection.
1973-1976 long jump seats. slanted at the front to accommodate front seats, single armrest, no leg, rest on bump stop. Note that up to 74 the frame was painted gray/metallic and from 1975 black.
1977 to ? long jump seat, I call them the...