Bocama did not make TUBING so I think you likely possibilities are
Reynolds (Zeus used this mostly, but not so sure about Razesa)
Columbus (they made metric tubing)
French-made brands, such as Vitus/Durifort
Besides measuring the ODs of the 3 main tubes, you should also investigate the inside "butt" or bottom of the fork's steerer: look for 5 shallow spirals...carefully examine the steerer for any BRANDING on the outside, such as a Columbus DOVE or the name REYNOLDS...the stamps, if there, will be very faint so use strong light.