This page describes four Gibson flat top acoustics, the J40, J45, J50 and J55 - though the J50 is not pictured.
UK prices (1981) were as follow: J40, £789; J45, J50 and J55, £829.
$8995
$8899
$6594
$6500
$6300
$5500
$5100
$5000
$4985
$4950
$4395
$4250
$4250
$4200
$4200
$4000
$3995
$3900
$3750