GZ34 BY LA RADIOTECHNIQUE RFT OR EI
Now this is a bit of an enigma because I don't know who has made it. This GZ34 dates from the 1970s and are from a small scale manufacturer of radiograms who went on to design and produce Amstrad's first transistor amplifier.
The envelope carries white print and a coding FJ - a La Radiotechnique factory code but from electrode cage structure may also be Yugoslav EI devices. Whoever the manufacturer, its a wonderful strong device available at a very keen price for a vintage high performance rectifier.