This is matched quartet of Raytheon RK 75 (307A, VT225). This
is very rare version of 307A, with just three ribs, all other versions have 5
ribs. This tube is also characteristic for double symmetrical getters.
This is matched quartet of Raytheon RK 75 (307A, VT225). This
is very rare version of 307A, with just three ribs, all other versions have 5
ribs. This tube is also characteristic for double symmetrical getters.