According to the
6x7 Extension Tube Manual, the 200mm with 3+2+1 extension tubes has a 0.59 magnification with a 34in (86.5cm) film to subject distance.
You can calculate the extension tube magnification as follows:
M = ( ML X F) + E / F
Where:
M = Magnification
ML = Magnification of the lens
F = Focal length
E = Extension tube length in mm
For the 200mm f4 lens, ML = 0.10 and 3+2+1 extension tubes = 56 + 28 + 14 = 98mm. But note this is for the Takumar and 6x7 generation of the 200mm. The 67 generation can focus closer.
M = [(0.1)(200) + 98 ] / 200 = 0.59